Question about Lincoln Navigator

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Replaced ride height sensors and compressor. At factory settings, vehicle kneels too low and does not achieve correct trim height. Me and my tech have adjusted the trim height on both front and rear manually with scan tool. 3 questions: 1) Do you have the correct factory TRIM ride height numbers to start from? 2) can the KNEEL height be adjusted seperately from the TRIM height. 3) Can you prevent the vehicle form kneeling? Thanks, Greg - Lincoln Mercury

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  • greg328 Sep 30, 2010

    Its a 2003 Gator with 4WAS, no bags. I need the actual factory TRIM settings (mm) for front and rear to compare to the setting we have currently programmed with the WDS. My other question was can you adjust the KNEEL ride height as well as the TRIM ride height? I have already figured out that if I want the vehicle to stop kneeling to disengage the switch, which in turn a code.

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  • Lincoln Master
  • 75,797 Answers

I have repaired dozens of these air suspension problems and without a doubt the #1 cause is leaking air bags, which you make no mention of replacing, as far as the changes to the ride height programs go they are preset and not adjustable, nor do i recommend you try and alter the system by fooling around with the ride height sensors, any changes u may attempt to make can and will adversely affect handling. My experience? 35 years as a Ford dealer factory trained and certified master technician in all phases of this system.

Posted on Sep 30, 2010

  • yadayada
    yadayada Sep 30, 2010

    Continued

  • yadayada
    yadayada Sep 30, 2010

    it has air suspension air bags, also known as air springs, not evwen sure what year and msoel this is now, please clarfiy, if it will not hold ride height then the air springs are leaking.

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Front end air suspension in cold weather acts up. I am in FL so I cannot imagine what it would do up north. It will correct itself after it has warmed up. The check air suspension message does NOT come on....


year?

SECTION 204-05: Vehicle Dynamic Suspension — 4-Wheel 2003 Expedition/Navigator Workshop Manual
DESCRIPTION AND OPERATION Vehicle Dynamic Suspension The four wheel air suspension system is comprised of the following components:
  • service switch
  • control module
  • two front height sensors
  • one rear height sensor
  • compressor and drier assembly (includes vent solenoid)
  • air lines
  • front and rear air spring and shock absorber assemblies
  • four air spring solenoids
-------------------------------------------------------------------------------
Principles of Operation
The 4-wheel air suspension (4WAS) module commands changes in vehicle height that are necessary for both the load leveling and the vertical height adjustment features.
The 4WAS load leveling feature automatically makes adjustments in vehicle height so that the vehicle is always at trim height, and that constant front-to-rear vehicle attitudes are maintained over the load range of the vehicle. Adjustments in height that are necessary to correct height differences between the vehicle left and right sides for the 4WAS system are restricted to what can be reliably achieved with three height sensors.
The height adjustment feature has three vehicle heights within a two-inch span:
Kneel height — improves the ease of entering and exiting by lowering the vehicle one inch below the trim height in the front and rear when the vehicle ignition is in the OFF or LOCK positions and the vehicle is stationary.
Trim height — normal vehicle ride position; vehicle moves to trim position when the ignition is ON, when the transmission is initially shifted to DRIVE or REVERSE mode, when all doors are closed or when speed of more than 24 km/h (15 mph) is detected.
Off-road height — improves ground clearance by raising the vehicle one inch above trim height in the front and rear when the vehicle is at 4x4 low modes and the vehicle speed is less than 40 km/h (25 mph).
The 4WAS module uses the universal bus protocol, (UBP), module communications network for sending and receiving various signals with the exception of speed, information from the three height sensors, and the air suspension service switch. For additional information about UBP, refer to Section 418-00 .
The 4WAS system holds vehicle height when any door or rear hatch is opened. The system stores front and rear vehicle height the moment any door is detected open. The system then maintains this height regardless of the addition or removal of a load. The system returns to its commanded height when all doors are closed or vehicle speed exceeds 24 km/h (15 mph).

---------------------------------------------------------------
Air Suspension Service Switch
The air suspension service switch signal is needed to wake up the 4WAS module. Without the module receiving this signal, the 4WAS system is inoperative at speeds below 24 km/h (15 mph) and will not react when the vehicle is raised or lowered. At speeds above 24 km/h (15 mph), the system will be active as if the air suspension service switch is in the ON position.
---------------------------------------------------------
Air Compressor
The air compressor:
  • consists of the compressor and vent solenoid; neither are replaceable as individual items.
  • is a single cylinder electric motor driven unit that provides pressurized air as required.
  • is powered by a solid state relay, which is controlled by the 4WAS module.
  • passes pressurized air through the compressor air drier that contains silica gel (a drying agent). Moisture is then removed from the compressor air drier when vented air passes out of the system during vent operation.
  • has a single port drier that can be replaced separately.
The vent solenoid:
  • allows air to escape from the system during venting actions.
  • is part of the air compressor cylinder head.
  • shares a common electrical connector with the air compressor motor.
  • is enclosed in the cylinder head casting, which forms an integral valve housing that allows the valve tip to enter the pressurized side of the system.
  • has an O-ring seal that prevents air leakage past the valve tip.
  • opens when the 4WAS module determines that lowering is required.
  • provides an escape route for pressurized air when system pressures exceed safe operating levels.
  • has a 1034 kPa (150 psi) internal relief valve.
  • is installed with the air compressor as a unit.
Air Spring
The 4WAS system has front and rear air springs. The air springs provide a varying spring rate proportional to the system's air pressure and volume. The air suspension system regulates the air pressure in each air spring by compressing and venting the system's air. Increasing air pressure (compressing) raises the vehicle; decreasing air pressure (venting) lowers the vehicle. Vehicle height is maintained by the addition and removal of air in each air spring through an air spring solenoid installed in the upper spring cap and energized through the 4WAS module command.
Air Lines and Fittings
NOTE: Apply a soapy water solution to the air lines to verify the location of air leaks. If the air lines are cut, ruptured or leaking, a service repair kit is available.
Nylon air lines with quick connect fittings connect to the air compressor and air spring solenoids. The compressor assembly output line is divided by the use of a fitting to supply the front and rear air springs. Fittings are also used to divide the air supply to the RH and LH air spring solenoids.
Air Suspension Height Sensors
There are two sensors used for the front suspension and one sensor used for the rear suspension. The sensors send a voltage signal to the 4WAS module. The output ranges from approximately 4.50 volts at minimum height (when the vehicle is low or in full jounce) to 0.50 volt at maximum height (when the vehicle is high or in full rebound). The sensors have a usable range of ± 45° compared to total suspension travel of 196 mm (7.84 in) at the front wheels and 240 mm (9.6 in) at the rear wheels. Therefore, the sensors are mounted to the suspension at a point where full suspension travel at the wheel is relative to the travel at the height sensor. The front height sensors are mounted to the frame and the links are attached to the upper arm ball studs. The rear height sensor is mounted to the frame and the link is attached to the rear lower arm ball stud.
When the height sensor indicates that the vehicle is lower than trim under normal driving conditions, the air compressor will turn on and pump compressed air to the system. When the sensor indicates that the vehicle is raised above trim under normal driving conditions, this will cause the air to be vented from the system to lower the vehicle to its trim height level.
Compressor Relay
A solid state relay is used in the air suspension system for compressor control. The relay incorporates a custom power metal oxide semi-conductor field effect transistor (MOSFET) and ceramic hybrid circuitry. The relay switches high current loads in response to low power signals and is controlled by the logic of the 4WAS module.
The compressor solid state relay is energized by the 4WAS module to have high current flow from the battery to the compressor motor.
4-Wheel Air Suspension (4WAS) Module
NOTE: The 4WAS module must receive a ride height adjustment calibration and must pass a pneumatic test when it is installed new or swapped.
The 4-wheel air suspension (4WAS) module controls the air compressor motor (through a solid state relay), all air spring solenoids, and provides power to front and rear height sensors. The 4WAS module also controls vehicle height adjustments by monitoring the three height sensors and other universal bus protocol (UBP) signals. The 4WAS module conducts all fail-safe and diagnostic strategies, and contains self-test and communication software for testing the vehicle and related components.
The 4WAS module monitors and controls the air suspension system through a 26-pin, two-way connector. The 4WAS module is keyed so that it cannot be plugged into an incorrect harness. There are two harness hardshell connectors and each is uniquely colored and keyed to prevent reversed connections.
-----------------------
  • The air compressor continuously cycles with the ignition switch in the OFF position and no DTC is set
  • Circuitry.
  • Air suspension relay.
  • 4WAS module.

Oct 21, 2009 | Lincoln Navigator Cars & Trucks

3 Answers

The rear suspension air bags no work


start here

The air suspension system is designed to improve ride, handling and general vehicle performance for static, on-road and off-road driving condition:
  • Ride is improved by using an air type spring (the soft ride is inherent).
  • Handling is improved by maintaining constant vehicle attitude.
The system consists of unique rear air springs, air compressor, air lines, air spring solenoids, height sensor, air suspension control module, attachments and associated signals derived from both driver and road inputs. With these components and signals, the air suspension control module commands changes in vehicle height that are necessary for the load leveling features.
The load leveling feature rear air suspension (RAS) systems shall automatically make adjustments in vehicle height so that the vehicle is always at trim height and constant front-to-rear vehicle attitudes are maintained over the expected load range of the vehicle. Adjustments in height that are necessary to correct height differences between the vehicle's left and right sides for RAS system shall be restricted to what can be reliably achieved with one air suspension height sensor.
The system uses one air suspension height sensor, a steering sensor, generic electronic module (GEM) transfer case inputs, and other vehicle sensors to measure driver and road inputs. The system changes vehicle height using an air compressor, two air lines, and the use of an air spring with an air spring solenoid.
The air suspension system holds vehicle height when the rear hatch or any door is opened. The system stores rear vehicle height the moment any open door is detected. The system then maintains this height regardless of the addition or removal of a load. The system will return to its commanded height when all doors are closed and the vehicle speed exceeds 16 km/h (10 mph).
Air Suspension Switch
The air suspension switch is located behind the RH kick panel on a mounting bracket. The switch interrupts power to the air suspension control module.
The air suspension switch supplies a signal to the air suspension control module. Without the air suspension control module receiving this signal the load leveling system is inoperative and will not react when rear of the vehicle is raised or lowered. If the air suspension system is disabled by turning off air suspension switch, a "CHECK SUSP" will appear in the RH corner of the instrument cluster with the ignition in the run position.
Air Compressor
The RAS air compressor:
  • Is not interchangeable with four wheel air suspension (4WAS) compressor.
  • Consists of the compressor and vent solenoid; neither are replaceable as individual items.
  • Is mounted in the engine compartment between the washer fluid bottle and headlamp (RH front corner).
  • Is a single cylinder electric motor driven unit that provides pressurized air as required.
  • Is powered by a solid state relay, controlled by the air suspension control module.
  • Passes pressurized air through the compressor air drier that contains silica gel (a drying agent). Moisture is then removed from the compressor air drier when vented air passes out of the system during vent operation.
  • Air drier has a single port and is not interchangeable with 4WAS compressor air drier.
  • Air drier may be replaced separately.
  • Incorporates a snorkle that may be replaced separately.
The vent solenoid:
  • Allows air to escape from the system during venting actions.
  • Is located in the air compressor cylinder head.
  • Has a 160 psi internal relief valve.
  • Shares a common electrical connector with the air compressor motor.
  • Is enclosed in the cylinder head casting, which forms an integral valve housing that allows the valve tip to enter the pressurized side of the system.
  • Has an O-ring seal that prevents air leakage past the valve tip.
  • Opens when the air suspension control module determines lowering is required.
  • Provides an escape route for pressurized air that opens when system pressures exceed safe operating levels.
  • Is replaced with the air compressor as a unit.
Air Spring
RAS vehicles use air springs in the rear. The air springs provide a varying spring rate proportional to the systems air pressure and volume. The air suspension system regulates the air pressure in each air spring by compressing and venting the system air. Increasing air pressure (compressing) raises the rear of the vehicle while decreasing air pressure (venting) lowers the rear of the vehicle. Vehicle height is maintained by the addition and removal of air in each air spring through an air spring solenoid installed in the upper spring cap and energized through the air suspension control module.
The air springs are mounted between the axle spring seats and the frame upper spring seats.
The two air springs replace the conventional rear coil springs.
Air Suspension Height Sensor
When the air suspension height sensor indicates that the rear of the vehicle is lower than trim under normal driving conditions, the air compressor will turn on and pump compressed air to the air springs. When the sensor indicates that the rear of the vehicle is raised above trim under normal driving conditions, this will cause the air to be vented from the air springs to lower the vehicle back to its trim height level.
One air suspension height sensor is mounted on the vehicle. The air suspension height sensor sends a voltage signal to the air suspension control module. The output ranges from approximately 4.75 volts at minimum height (when the vehicle is low or in full jounce), to 0.25 volts at maximum height (when the vehicle is high or in full rebound). The air suspension height sensor has a useable range of 80 mm (3 in) compared to total suspension travel of 200-250 mm (8 to 10 in) at the wheel. Therefore, the air suspension height sensor is mounted to the suspension at a point where full rear suspension travel at the wheel is relative to 80 mm of travel at the air suspension height sensor. The air suspension height sensor is attached between the No. 5 frame crossmember (upper socket) and the panhard rod (lower socket). Replace the air suspension height sensor as a unit.
Compressor Relay
The compressor relay is energized by the air suspension control module to allow high current to flow from the battery to the compressor motor.
  • A solid state relay is used in the air suspension system for air compressor control. The relay incorporates a custom power metal oxide semi-conductor field effect transistor (MOSFET) and ceramic hybrid circuitry. The relay switches high current loads in response to low power signals and is controlled by the logic of the air suspension control module.
Air Suspension Control Module
NOTE: The 4WAS air suspension control module is used for the RAS system. The internal processor recognizes external circuitry to determine if it is installed in a 4WAS or a RAS equipped vehicle.
NOTE: The air suspension control module is calibrated with information from the air suspension height sensor. A new or exchanged air suspension control module requires a ride height adjustment calibration process to be performed.
The air suspension control module controls the air compressor motor (through a solid state relay), and the air spring solenoids. The air suspension control module also provides power to the air suspension height sensor. The air suspension control module controls vehicle height adjustments by monitoring the air suspension height sensor, vehicle speed, a steering sensor, acceleration input, the door ajar signal, transfer case signals, and the brake pedal position (BPP) switch. The air suspension control module also conducts all fail-safe and diagnostic strategies and contains self-test and communication software for testing of the vehicle and related components.
The air suspension control module is mounted in the passenger compartment inside the instrument panel above the radio and temperature controls.
The air suspension control module monitors and controls the air suspension system through a 32-pin two-way connector. The air suspension control module is keyed so that the air suspension control module cannot be plugged into an incorrect harness. There are two sides of the harness connection to the air suspension control module. Each is uniquely colored and keyed to prevent reversing the connections.
Air Suspension Diagnostic Connector
The air suspension diagnostic connector is used to aid the technician in diagnosing the air suspension system. It is also used to vent the system of compressed air when air suspension system components need to be repaired or replaced. The air suspension diagnostic connector is located under steering column.

Oct 02, 2009 | 1998 Ford Expedition

2 Answers

Can any one tell me were how i can find the automatic level control on my 1994 town car


Description and Operation The rear air suspension:
  • Is an air-operated, microprocessor-controlled, suspension system.
  • Replaces the conventional rear coil spring suspension.
  • Provides low spring rates for improved ride and automatic rear load leveling.
  • Is standard equipment on the Town Car.
  • Is available as optional equipment on Crown Victoria and Grand Marquis.
The rear air suspension system has the following features:
  • The system is operational with the ignition switch in the RUN position.
  • Automatic rear load leveling has limited operation for one hour after ignition switch is turned to OFF.
  • The air suspension switch, located on the right side of the luggage compartment, must be turned OFF when the vehicle is on a hoist, being towed or jump started.
  • The Air Suspension warning indicator is located in the instrument panel, to the right of the speedometer.
    • The warning indicator flashes five times and then stays on when service switch is turned off or a system malfunction is detected.
  • The rear leveling system operates by adding or removing air in the springs to maintain the level of the vehicle at a predetermined rear suspension D ride height dimension, and is controlled by a control module (5A919) .
  • The rear air suspension control module also controls the electronic variable orifice (EVO) steering.
  • Refer to Section 11-02 for Description of the EVO steering system.
  • Air required for leveling the vehicle is distributed from the air compressor to the rear air springs by a nylon air line which runs from the compressor air dryer (5346) through a Y-fitting to each individual air spring.


Suspension, Computer Controlled—Town Car

c441c13.gif
Item Part Number Description 1 9C392 Compressor Relay Power Junction Block 2 5A897 Air Line (Attached to Brake/Fuel Bundle) 3 5319 Air Compressor With Regenerative Air Dryer and Vent Solenoid 4 5A897 Air Line to Compressor 5 5K761 Air Suspension Service Switch 6 14489 Data Link Connector 7 — Quick Connect 8 — To LH Air Spring 9 — From Compressor 10 — Y-Fitting (Part of 5A911) 11 — To RH Air Spring 12 5A908 Heat Shield 13 5A966 Spring Retainer Clip 14 5560 Rear Spring 15 5359 RearAir Suspension Height Sensor 16 5A919 Control Module 17 14018 Air Spring Solenoid

Control Module Power and Ground The control module (5A919) has the following features:
  • Power is provided by Circuit 418 and is controlled by the air suspension switch.
    • The air suspension switch is powered through a 15 amp fuse in Circuit 296 in Town Car.
    • AIR SUSPN PUMP (30A MAXI) fuse provides this power through Circuit 414 in the Crown Victoria/Grand Marquis.
  • Control module ground is provided through control module wire harness Pins 6 and 21, to the RH inner quarter panel sheet metal, near the control module .
---------------------------------
Weight Added When weight is added to the vehicle:
  • The air suspension height sensor (5359) length is reduced from trim length, sending a "rear is low" signal to the control module (5A919).
  • The control module then turns the compressor on by grounding the compressor relay control Circuit 420. This restores the rear of the vehicle to trim position.
    • Battery voltage is provided to the relay coil by Circuit 414.
  • The control module opens the spring solenoid valves (5311) by switching Circuits 416 and 429 to ground. This allows pressurized air to enter the springs.
    • Battery voltage is provided to the air spring solenoid valves by Circuit 414.
  • Compressed air flows from the compressor, through the compressor air dryer (5346) airlines and spring solenoid valves into the rear springs (5560).
  • As the rear springs raise the rear body height, the air suspension height sensor increases in length until the preset trim height is reached.
  • The control module then turns off the compressor (through the relay) and closes the air spring solenoid valves.
----------------------------------------------------------------------
Weight Removed When weight is removed:
  • The air suspension height sensor (5359) length is increased from the trim length, sending a "rear is high" signal to the control module (5A919).
  • The control module then opens the vent solenoid valve (located in the compressor assembly) by switching Circuit 421 to ground and opens the solenoid valves (5311) by switching Circuits 416 and 429 to ground. This restores the rear of the vehicle to trim position.
  • Compressed air flows from rear springs (5560), through the air spring solenoid valves, air lines, compressor air dryer (5346), and out the vent solenoid valve.
  • As the body lowers, the air suspension height sensor length decreases until the preset trim height is reached.
  • The control module then closes the vent and solenoid valves.
-----------------------------------------
Control module operates as follows:
  • In general the control module uses a 45-second averaging interval to determine when compress and vent operations are needed.
  • However, door courtesy lamp switch (13713) inputs can override the 45-second averaging interval so compress and vent operations can begin immediately, if needed.
  • The 45-second averaging interval is used to keep the control module from making unneeded corrections.
  • When a vehicle at the correct rear trim height hits a bump, the air suspension height sensor output will read low and high in addition to trim until the oscillations die out.
  • If the control module were to correct for these "bump induced readings", system duty cycle would increase unnecessarily.
  • The 45-second averaging interval not only eliminates corrections due to bumps, but also eliminates unneeded corrections resulting from braking, accelerating, and turning. The control module tabulates the air suspension height sensor readings, and does not begin a compress or vent operation until the air suspension height sensor (5359) reads low or high for 45 seconds consistently.
  • There are more restrictions on vent operations than there are on compress operations.
  • To eliminate the chance of catching a door on a curb as the vehicle vents down, the control module will not allow any venting to occur when a door is open.
  • The control module does not allow any vent operations for the first 45 seconds after the ignition switch (11572) has been turned to RUN.
    • Even if a vehicle is extremely high in the rear, DO NOT expect it to vent until the ignition switch has been turned to RUN for 45 seconds.

Jun 24, 2009 | 1994 Lincoln Town Car

1 Answer

REPLACED DRYER ON 96 CONT NOW THE BACK WONT AIR UP FRONT DOES


maybe you got dirt in the line to the rear. Here's some background info:

The air suspension system includes the following major components:
  • Air compressor to supply air to the air springs (part of front spring and shock and rear spring and shock absorber assemblies
  • Front spring and shock (3C098) and rear spring and shock absorber (5A965) at each corner of the vehicle
  • Four linear air suspension height sensors (5359): two rear and two front height sensors to maintain the vehicle at the proper ride height; only LH rear height sensor is used for air suspension.
  • Dual-mode front spring and shock and rear shock absorber assemblies with internal actuator.
All system functions are controlled by vehicle dynamics control module (5A919). This control module receives inputs from several different sources. These inputs include:
  • vehicle speed via multiplex communication network
  • ignition switch position
  • door position via multiplex communication network
  • height sensor position
  • air suspension service switch
  • engine rpm via multiplex communication network
  • ride and steering personality settings via multiplex communications network
Communications monitor system operation and allow diagnosis of any concerns that may develop in the system.
  • System monitoring for the driver's use is provided through the instrument panel mounted message center indicator (10D898).
  • Diagnosis communication for the service technician is provided through the data link connector (14489) (DLC) under the instrument panel and Rotunda New Generation Star (NGS) Tester 007-00500 or equivalent.
The message center indicator will display AIR LEVELING DISABLED or CHECK RIDE CONTROL if the suspension system is not turned on or the vehicle dynamics control module detects a concern. If air leveling system disabled is displayed, check that air suspension service switch is in the ON position.
-------------------------------------------------------
Weight Added When weight is added to the vehicle, the air suspension system responds as follows:
  • Air suspension height sensor length is reduced from trim length, sending a "vehicle is low" signal to the vehicle dynamics control module (5A919).
  • To restore vehicle to the trim position, the vehicle dynamics control module turns the compressor on by grounding the compressor relay control Circuit 420 (DB/Y). The relay is ground-side switched.
  • To allow pressurized air to enter the rear spring (5560) and front spring and shock (3C098), the control module opens the solenoid valves (5311).
  • Compressed air flows from the compressor, through the compressor air drier assembly, air lines and solenoid valves into the air springs.
  • As the air springs raise the body height, the air suspension height sensor (5359) increases in length until the preset trim height is reached.
  • The vehicle dynamics control module then turns off the compressor (through the relay) and closes the air spring solenoid valves.
  • ----------------------------------------------------------------------------
  • Weight Removed When weight is removed, the air suspension system responds as follows:
    • Air suspension height sensor length is increased from the trim length, sending a "vehicle is high" signal to the control module (5A919).
    • To restore the vehicle to the trim position, the vehicle dynamics control module opens the vent solenoid valve (located in the compressor assembly) and opens the solenoid valves (5311).
    • Compressed air flows from air springs, through the solenoid valves, air lines, compressor air drier (5346) and out the vent solenoid valve.
    • As the body lowers, the air suspension height sensor length decreases until the preset trim height is reached.
    • The vehicle dynamics control module then closes the vent and solenoid valves.
------------------------------------------------------------------------------
Control Module Power and Ground The vehicle dynamics control module (5A919) is located above the upper luggage compartment trim panel and lower module tray. Module power is provided by Circuit 418 (DG/Y) at Pins 36, 37, 56, 57, 58 and is powered through a Fuse 7 (30A) in power distribution box. Module ground is provided through control module wire harness Pins 6, 39, 40 and 60. The data link connector (14489) (DLC) is located in the passenger compartment under the instrument panel, 300 mm (12 inches) right of the steering column. This connector allows communications between the vehicle dynamics control module and either Rotunda New Generation Star (NGS) Tester 007-00500 or equivalent or Rotunda Service Bay Diagnostics System (SBDS)® 001-00001 or equivalent. When the CHECK RIDE CONTROL message is displayed in the message center indicator (10D898), a system error has been detected by the vehicle dynamics control module and is stored in the control module. This diagnostic trouble code (DTC) will be retained for the next 80 ignition switch cycles. If there is no repeat of the same error during these 80 ignition switch cycles, the control module will erase the DTC. Because of this self-erasing memory, a customer may have had a concern "just a few days ago" that is not retrieved from memory when Diagnostic Test Mode (DTC) "Retrieve/Clear Continuous DTCs" is executed. This must be kept in mind if you must tell customer that no current concern has been found. When the vehicle dynamics control module detects a concern, the air suspension system is disabled for the current ignition cycle. If the condition causing the concern clears up during the current ignition switch cycle, the system will not reactivate. For example, if the customer has severely overloaded the luggage compartment, the system will not be able to trim the vehicle without exceeding the compressor run time. This will generate a DTC that disables the computer controlled suspension system. If the customer then drives the vehicle and unloads the luggage compartment without turning the ignition switch OFF, the system will not adjust for the new load. The customer will experience poor ride quality and the vehicle will not adjust trim.

May 20, 2009 | 1996 Lincoln Continental

2 Answers

No power to rear bags its down but wont air up bags dont seem cracked unplugged connector no power I tried resetting still no power


is switch on?
The air suspension switch and bracket is mounted below the RH side of the instrument panel.

Dealer can run diagnostic test with scan tool for fault codes.
----------

The air suspension system is designed to improve ride, handling and general vehicle performance for static, on-road and off-road driving conditions:
  • Ride is improved by using an air type spring (the soft ride is inherent).
  • Handling is improved by maintaining constant vehicle attitude.
The system consists of unique rear air springs, the air compressor, air lines, air spring solenoids, height sensor, air suspension control module, attachments and associated signals derived from both driver and road inputs. With these components and signals, the air suspension control module commands changes in vehicle height that are necessary for the load leveling features.
The load leveling feature rear air suspension (RAS) systems shall automatically make adjustments in vehicle height so that the vehicle is always at trim height and constant front-to-rear vehicle attitudes are maintained over the expected load range of the vehicle. Adjustments in height that are necessary to correct height differences between the vehicle's left and right sides for the RAS system shall be restricted to what can be reliably achieved with one air suspension height sensor.
The system uses one air suspension height sensor, a steering sensor, generic electronic module (GEM) and other vehicle sensors to measure driver and road inputs. The system changes vehicle height using an air compressor, two air lines and the use of air springs with air spring solenoids.
The air suspension system holds vehicle height when the rear hatch or any door is opened. The system stores rear vehicle height the moment any open door is detected. The system then maintains this height regardless of the addition or removal of a load. The system will return to its commanded height when all doors are closed or the vehicle speed exceeds 16 km/h (10 mph).
------------------------------------
Air Spring
RAS vehicles use air springs in the rear. The air springs provide a varying spring rate proportional to the systems air pressure and volume. The air suspension system regulates the air pressure in each air spring by compressing and venting the system air. Increasing air pressure (compressing) raises the rear of the vehicle while decreasing air pressure (venting) lowers the rear of the vehicle. Vehicle height is maintained by the addition and removal of air in each air spring through an air spring solenoid installed in the upper spring cap and energized through the air suspension control module.
The two air springs support the conventional rear leaf coil springs.
Air Suspension Height Sensor
One air suspension height sensor is mounted on the vehicle. The air suspension height sensor sends a voltage signal to the air suspension control module. The output ranges from approximately 4.75 volts at minimum height (when the vehicle is low or in full jounce), to 0.25 volts at maximum height (when the vehicle is high or in full rebound). The air suspension height sensor has a useable range of 80 mm (3.2 in) compared to total suspension travel of 200-250 mm (8 to 10 in) at the wheel. Therefore, the air suspension height sensor is mounted to the suspension at a point where full rear suspension travel at the wheel is relative to 80 mm (3.2 in) of travel at the air suspension height sensor. The air suspension height sensor is attached between the No. 5 frame crossmember (upper socket) and the panhard rod (lower socket).
When the air suspension height sensor indicates that the rear of the vehicle is lower than trim under normal driving conditions, the air compressor will turn on and pump compressed air to the air springs. When the sensor indicates that the rear of the vehicle is raised above trim under normal driving conditions, this will cause the air to be vented from the air springs to lower the vehicle back to its trim height level.
Compressor Relay
The compressor relay is energized by the air suspension control module to allow high current to flow from the battery to the compressor motor.
  • A solid state relay is used in the air suspension system for air compressor control. The relay incorporates a custom power metal oxide semi-conductor field effect transistor (MOSFET) and ceramic hybrid circuitry. The relay switches high current loads in response to low power signals and is controlled by the logic of the air suspension control module.
Air Suspension Control Module
NOTE: The 4WAS air suspension control module is used for the RAS system. The internal processor recognizes external circuitry to determine if it is installed in a 4WAS or a RAS equipped vehicle.
NOTE: The air suspension control module is calibrated with information from the air suspension height sensor. A new or exchanged air suspension control module requires a ride height adjustment calibration process to be performed.
The air suspension control module controls the air compressor motor (through a solid state relay), and the air spring solenoids. The air suspension control module also provides power to the air suspension height sensor. The air suspension control module controls vehicle height adjustments by monitoring the air suspension height sensor, vehicle speed, a steering sensor, acceleration input, the door ajar signal, transfer case signals, and the brake pedal position (BPP) switch. The air suspension control module also conducts all fail-safe and diagnostic strategies and contains self-test and communication software for testing the vehicle and related components.
The air suspension control module monitors and controls the air suspension system through a 32-pin two-way connector. The air suspension control module is keyed so that the air suspension control module cannot be plugged into an incorrect harness. There are two sides of the harness connection to the air suspension control module. Each is uniquely colored and keyed to prevent reversing the connections.
------------------------------------------------------------------------
Visual Inspection Chart Mechanical Electrical
  • Restricted suspension movement
  • Excessive vehicle load
  • Cut, severed or crimped air line(s)
  • Unmounted height sensor
  • Damaged air spring(s)
  • Open fuses:
    • Central junction box (CJB) Fuse 4 (15A), 6 (5A) and 20 (5A)
    • Battery junction box (BJB) Fuse 109 (50A)
  • Loose, corroded or disconnected connectors
  • Air suspension switch is in the OFF position
  • Damaged solenoid valve(s)


-----------------------------------------------------------
  • The compressor is inoperative
  • BJB Fuse 109 (50A).
  • Air compressor assembly.
  • Circuitry.
  • Air suspension relay.

Apr 30, 2009 | 2000 Ford Expedition

5 Answers

Lincoln navigator air suspension is all the way down


that should not happen. Did you turn the switch off in the back for the suspension? Did you do something else at the same time, like check the spare tire for air pressure?

I have info on 2003 navigator 4 wheel air suspension. Maybe similar

SECTION 204-05: Vehicle Dynamic Suspension — 4-Wheel 2003 Expedition/Navigator Workshop Manual
DESCRIPTION AND OPERATION Vehicle Dynamic Suspension The four wheel air suspension system is comprised of the following components:
  • service switch
  • control module
  • two front height sensors
  • one rear height sensor
  • compressor and drier assembly (includes vent solenoid)
  • air lines
  • front and rear air spring and shock absorber assemblies
  • four air spring solenoids
WARNING: The service switch for the air suspension system must be shut off prior to hoisting, jacking or towing an air suspension vehicle. This can be accomplished by turning off the air suspension switch located in the jack storage area in the rear of the passenger compartment. Failure to do so may result in unexpected inflation or deflation of the air springs which may result in shifting of the vehicle during these operations.

WARNING: Do not remove an air spring under any circumstances when there is pressure in the air spring. Do not remove any components supporting an air spring without either exhausting the air or providing support for the air spring to prevent vehicle damage or personal injury.

Air Suspension Pneumatic Diagram 801e0c4.gif
Item Part Number Description 1 5319 Air compressor and drier 2 5B322 Air line T-fitting 3 5B321 Air line union 4 — Air line Y-fitting 5 18945/5311 Air spring and solenoid
------------------------------
Principles of Operation
The 4-wheel air suspension (4WAS) module commands changes in vehicle height that are necessary for both the load leveling and the vertical height adjustment features.
The 4WAS load leveling feature automatically makes adjustments in vehicle height so that the vehicle is always at trim height, and that constant front-to-rear vehicle attitudes are maintained over the load range of the vehicle. Adjustments in height that are necessary to correct height differences between the vehicle left and right sides for the 4WAS system are restricted to what can be reliably achieved with three height sensors.
The height adjustment feature has three vehicle heights within a two-inch span:
Kneel height — improves the ease of entering and exiting by lowering the vehicle one inch below the trim height in the front and rear when the vehicle ignition is in the OFF or LOCK positions and the vehicle is stationary.
Trim height — normal vehicle ride position; vehicle moves to trim position when the ignition is ON, when the transmission is initially shifted to DRIVE or REVERSE mode, when all doors are closed or when speed of more than 24 km/h (15 mph) is detected.
Off-road height — improves ground clearance by raising the vehicle one inch above trim height in the front and rear when the vehicle is at 4x4 low modes and the vehicle speed is less than 40 km/h (25 mph).
The 4WAS module uses the universal bus protocol, (UBP), module communications network for sending and receiving various signals with the exception of speed, information from the three height sensors, and the air suspension service switch. For additional information about UBP, refer to Section 418-00 .
The 4WAS system holds vehicle height when any door or rear hatch is opened. The system stores front and rear vehicle height the moment any door is detected open. The system then maintains this height regardless of the addition or removal of a load. The system returns to its commanded height when all doors are closed or vehicle speed exceeds 24 km/h (15 mph).

-------------------------------
Air Suspension Service Switch
The air suspension service switch signal is needed to wake up the 4WAS module. Without the module receiving this signal, the 4WAS system is inoperative at speeds below 24 km/h (15 mph) and will not react when the vehicle is raised or lowered. At speeds above 24 km/h (15 mph), the system will be active as if the air suspension service switch is in the ON position.
Vehicles without message center When the air suspension service switch is in the OFF position and the ignition switch is in the RUN position, a "CHECK SUSP" will appear in the RH corner of the instrument cluster.
Vehicles with message center When the air suspension service switch is in the OFF position and the ignition switch is in the RUN position, the message center will display "SUSPENSION SWITCHED OFF"
-------------------------------------------
Inspection and Verification
  1. Verify the customer concern.
  1. NOTE: If the door ajar indicator is illuminated when all doors, liftgate, and liftgate glass are closed, the air suspension will not work correctly. Repair door ajar indicator; refer to Section 413-01 .
    Visually inspect for obvious signs of mechanical and electrical damage.


Visual Inspection Chart Mechanical Electrical
  • Restricted suspension movement
  • Excessive vehicle load
  • Cut, severed, crimped air line(s)
  • Unmounted height sensor(s)
  • Damaged front air spring(s)
  • Damaged rear air spring(s)
  • Battery junction box (BJB) fuses 20 (30A), fuse 27 (5A), and fuse 111 (50A)
  • Loose, corroded, or disconnected connectors
  • Air suspension service switch is in the OFF position
  • Damaged solenoid valve(s)

-------------------------
I fthis does not help, the dealer can hook up his diagnostic equipment and download fault codes. Good luck. Please give best rating if this helps.

Apr 20, 2009 | 2004 Lincoln Navigator

1 Answer

Airride suspension won't deflate only inflate


It will only process a "down command" if it thinks all the doors are closed. If you have a bad door switch, it won't lower. Any courtesy lights on with doors closed?
The dealer can conduct a diagnostic scan test and retrieve any codes that will help identify the bad circuit. Did they do that?

Do you have 4 wheel air suspension or just rear?

Assuming rear only:
The system consists of unique rear air springs, the air compressor, air lines, air spring solenoids, height sensor, air suspension control module, attachments and associated signals derived from both driver and road inputs. With these components and signals, the air suspension control module commands changes in vehicle height that are necessary for the load leveling features.
The load leveling feature rear air suspension (RAS) systems shall automatically make adjustments in vehicle height so that the vehicle is always at trim height and constant front-to-rear vehicle attitudes are maintained over the expected load range of the vehicle. Adjustments in height that are necessary to correct height differences between the vehicle's left and right sides for the RAS system shall be restricted to what can be reliably achieved with one air suspension height sensor.
The system uses one air suspension height sensor, a steering sensor, generic electronic module (GEM) and other vehicle sensors to measure driver and road inputs. The system changes vehicle height using an air compressor, two air lines and the use of air springs with air spring solenoids.

Note this section.
The air suspension system holds vehicle height when the rear hatch or any door is opened. The system stores rear vehicle height the moment any open door is detected. The system then maintains this height regardless of the addition or removal of a load. The system will return to its commanded height when all doors are closed or the vehicle speed exceeds 16 km/h (10 mph).

Air Suspension Switch
The air suspension switch supplies power to the air suspension control module. Without the air suspension control module receiving this power, the load leveling system is inoperative and will not react when the rear of the vehicle is raised or lowered. If the air suspension system is disabled by turning off the air suspension switch, a "CHECK SUSP" will appear in the RH corner of the instrument cluster with the ignition in the run position.
--------------------------------------------------------------------
The vent solenoid:
  • allows air to escape from the system during venting actions.
  • is part of the air compressor cylinder head.
  • has a 1,103 kPa (160 psi) internal relief valve.
  • shares a common electrical connector with the air compressor motor.
  • is enclosed in the cylinder head casting, which forms an integral valve housing that allows the valve tip to enter the pressurized side of the system.
  • has an O-ring seal that prevents air leakage past the valve tip.
  • opens when the air suspension control module determines lowering is required.
  • provides an escape route for pressurized air that opens when system pressures exceed safe operating levels.
  • is replaced with the air compressor as a unit.
---------------------------------------------------------------
Air Suspension Height Sensor
One air suspension height sensor is mounted on the vehicle. The air suspension height sensor sends a voltage signal to the air suspension control module. The output ranges from approximately 4.75 volts at minimum height (when the vehicle is low or in full jounce), to 0.25 volts at maximum height (when the vehicle is high or in full rebound). The air suspension height sensor has a useable range of 80 mm (3.2 in) compared to total suspension travel of 200-250 mm (8 to 10 in) at the wheel. Therefore, the air suspension height sensor is mounted to the suspension at a point where full rear suspension travel at the wheel is relative to 80 mm (3.2 in) of travel at the air suspension height sensor. The air suspension height sensor is attached between the No. 5 frame crossmember (upper socket) and the panhard rod (lower socket).
When the air suspension height sensor indicates that the rear of the vehicle is lower than trim under normal driving conditions, the air compressor will turn on and pump compressed air to the air springs. When the sensor indicates that the rear of the vehicle is raised above trim under normal driving conditions, this will cause the air to be vented from the air springs to lower the vehicle back to its trim height level.
Compressor Relay
The compressor relay is energized by the air suspension control module to allow high current to flow from the battery to the compressor motor.
  • A solid state relay is used in the air suspension system for air compressor control. The relay incorporates a custom power metal oxide semi-conductor field effect transistor (MOSFET) and ceramic hybrid circuitry. The relay switches high current loads in response to low power signals and is controlled by the logic of the air suspension control module.
Air Suspension Control Module
NOTE: The 4WAS air suspension control module is used for the RAS system. The internal processor recognizes external circuitry to determine if it is installed in a 4WAS or a RAS equipped vehicle.
NOTE: The air suspension control module is calibrated with information from the air suspension height sensor. A new or exchanged air suspension control module requires a ride height adjustment calibration process to be performed.
The air suspension control module controls the air compressor motor (through a solid state relay), and the air spring solenoids. The air suspension control module also provides power to the air suspension height sensor. The air suspension control module controls vehicle height adjustments by monitoring the air suspension height sensor, vehicle speed, a steering sensor, acceleration input, the door ajar signal, transfer case signals, and the brake pedal position (BPP) switch. The air suspension control module also conducts all fail-safe and diagnostic strategies and contains self-test and communication software for testing the vehicle and related components.
The air suspension control module monitors and controls the air suspension system through a 32-pin two-way connector. The air suspension control module is keyed so that the air suspension control module cannot be plugged into an incorrect harness. There are two sides of the harness connection to the air suspension control module. Each is uniquely colored and keyed to prevent reversing the connections.
---------------------------------------------------
May be a bad module too.

Apr 11, 2009 | 2000 Lincoln Navigator

1 Answer

EXPEDITION REAR AIR RIDE PROBLEM


do you have just rear air suspension? here's rear only. 4 wheel different. Deler an run a diagnostic test with WDS machine and get fault codes.
-------------------------------------------------------------------------------------
The air suspension system is designed to improve ride, handling and general vehicle performance for static, on-road and off-road driving conditions:
  • Ride is improved by using an air type spring (the soft ride is inherent).
  • Handling is improved by maintaining constant vehicle attitude.
The system consists of unique rear air springs, the air compressor, air lines, air spring solenoids, height sensor, air suspension control module, attachments and associated signals derived from both driver and road inputs. With these components and signals, the air suspension control module commands changes in vehicle height that are necessary for the load leveling features.
The load leveling feature rear air suspension (RAS) systems shall automatically make adjustments in vehicle height so that the vehicle is always at trim height and constant front-to-rear vehicle attitudes are maintained over the expected load range of the vehicle. Adjustments in height that are necessary to correct height differences between the vehicle's left and right sides for the RAS system shall be restricted to what can be reliably achieved with one air suspension height sensor.
The system uses one air suspension height sensor, a steering sensor, generic electronic module (GEM) and other vehicle sensors to measure driver and road inputs. The system changes vehicle height using an air compressor, two air lines and the use of air springs with air spring solenoids.
The air suspension system holds vehicle height when the rear hatch or any door is opened. The system stores rear vehicle height the moment any open door is detected. The system then maintains this height regardless of the addition or removal of a load. The system will return to its commanded height when all doors are closed or the vehicle speed exceeds 16 km/h (10 mph).
----------------------------------------------------------------------------------------
Air Suspension Height Sensor
One air suspension height sensor is mounted on the vehicle. The air suspension height sensor sends a voltage signal to the air suspension control module. The output ranges from approximately 4.75 volts at minimum height (when the vehicle is low or in full jounce), to 0.25 volts at maximum height (when the vehicle is high or in full rebound). The air suspension height sensor has a useable range of 80 mm (3.2 in) compared to total suspension travel of 200-250 mm (8 to 10 in) at the wheel. Therefore, the air suspension height sensor is mounted to the suspension at a point where full rear suspension travel at the wheel is relative to 80 mm (3.2 in) of travel at the air suspension height sensor. The air suspension height sensor is attached between the No. 5 frame crossmember (upper socket) and the panhard rod (lower socket).
When the air suspension height sensor indicates that the rear of the vehicle is lower than trim under normal driving conditions, the air compressor will turn on and pump compressed air to the air springs. When the sensor indicates that the rear of the vehicle is raised above trim under normal driving conditions, this will cause the air to be vented from the air springs to lower the vehicle back to its trim height level
------------------------------------------------------------------------------
  • Uneven vehicle height
  • Circuitry.
  • Rear pneumatic fault.
  • Air compressor assembly.
  • Air suspension control module.
  • Go To Pinpoint Test I .

Feb 21, 2009 | 2001 Ford Expedition

2 Answers

Where are the leveling sensors located on a 2003 Navigator?


There is one at each wheel. here is some info

Vehicle Dynamic Suspension The four wheel air suspension system is comprised of the following components:
  • service switch
  • control module
  • two front height sensors
  • one rear height sensor
  • compressor and drier assembly (includes vent solenoid)
  • air lines
  • front and rear air spring and shock absorber assemblies
  • four air spring solenoids
s3j~us~en~file=ani_caut.gif~gen~ref.gif WARNING: The service switch for the air suspension system must be shut off prior to hoisting, jacking or towing an air suspension vehicle. This can be accomplished by turning off the air suspension switch located in the jack storage area in the rear of the passenger compartment. Failure to do so may result in unexpected inflation or deflation of the air springs which may result in shifting of the vehicle during these operations.
s3j~us~en~file=ani_caut.gif~gen~ref.gif WARNING: Do not remove an air spring under any circumstances when there is pressure in the air spring. Do not remove any components supporting an air spring without either exhausting the air or providing support for the air spring to prevent vehicle damage or personal injury.
Air Suspension Pneumatic Diagram 17d59a6.gif
Item Part Number Description 1 5319 Air compressor and drier 2 5B322 Air line T-fitting 3 5B321 Air line union 4 — Air line Y-fitting 5 18945/5311 Air spring and solenoid

Suspension Height Sensor Removal and Installation
NOTE: Front shown, rear similar
  1. s3j~us~en~file=ani_caut.gif~gen~ref.gif WARNING: The electrical power to the air suspension system must be shut off prior to hoisting, jacking or towing an air suspension vehicle. This can be accomplished by turning off the air suspension switch located in the LH quarter trim panel. Failure to do so may result in unexpected inflation or deflation of the air springs which may result in shifting of the vehicle during these operations.
    Raise and support the vehicle. For additional information, refer to Section 100-02 .
  1. Disconnect the sensor arm. 721ed10.gif
3. Remove the bolts and the sensor. b198e3c.gif
4.
  1. Disconnect the electrical connector.
---------------------------------------------------------------------------------------------

Ride Height Adjustments
Special Tool(s) s3j~us~en~file=st2332a.gif~gen~ref.gif Worldwide Diagnostic System (WDS)
418-F224

New Generation STAR (NGS) Tester
418-F052 or equivalent scan tool
Inflation and Deflation of the Air Suspension System
  1. NOTE: Make sure that the air suspension switch is in the ON position
    NOTE: Make sure that a battery voltage of at least 11 volts is maintained while carrying out this procedure.
    Turn the ignition switch to the ON position.
  1. Connect scan tool to the data link connector (DLC).
  1. Select Air Suspension Control Module under Active Command Mode:
    • VENT FRNT to deflate the front down.
    • LIFT FRNT to inflate the front up.
    • VENT REAR to deflate the rear down.
    • LIFT REAR to inflate the rear up.
Calibration
Ride Height Resetting
  1. NOTE: Make sure that the air suspension switch is in the ON position
    NOTE: Make sure that a battery voltage of at least 11 volts is maintained while carrying out this procedure.
    Turn the ignition to the ON position.
    • Exit the vehicle, close all doors and allow the system to vent the vehicle down to kneel height (approximately 45 seconds).
  1. With the ignition remaining in the ON position, shift the vehicle into DRIVE and then back to PARK.
    • Exit the vehicle, close all doors and allow the vehicle to pump to trim (approximately 45 seconds).
  1. Measure the ride height. For additional information, refer to Section 204-00 .
  1. Open the LF door.
  1. Connect scan tool to the data link connector (DLC).
  1. While outside of the vehicle, select the proper vehicle year, model and engine type.
  1. Select 4WAS module.
  1. Using the active command mode, vent or lift the vehicle to achieve the correct ride height.
  1. Select the "Save Calibration Values (Store Ride Height)" scan tool command to calibrate the 4WAS module.
-------------------------------------------------------------------------------

Jan 09, 2009 | 2003 Lincoln Navigator

2 Answers

AIR SUSPENTION WORKS ABNORMALY


a lot of info here:
Principles of Operation
The 4-wheel air suspension (4WAS) module commands changes in vehicle height that are necessary for both the load leveling and the vertical height adjustment features.
The 4WAS load leveling feature automatically makes adjustments in vehicle height so that the vehicle is always at trim height, and that constant front-to-rear vehicle attitudes are maintained over the load range of the vehicle. Adjustments in height that are necessary to correct height differences between the vehicle left and right sides for the 4WAS system are restricted to what can be reliably achieved with three height sensors.
The height adjustment feature has three vehicle heights within a two-inch span:
Kneel height — improves the ease of entering and exiting by lowering the vehicle one inch below the trim height in the front and rear when the vehicle ignition is in the OFF or LOCK positions and the vehicle is stationary.
Trim height — normal vehicle ride position; vehicle moves to trim position when the ignition is ON, when the transmission is initially shifted to DRIVE or REVERSE mode, when all doors are closed or when speed of more than 24 km/h (15 mph) is detected.
Off-road height — improves ground clearance by raising the vehicle one inch above trim height in the front and rear when the vehicle is at 4x4 low modes and the vehicle speed is less than 40 km/h (25 mph).
The 4WAS module uses the universal bus protocol, (UBP), module communications network for sending and receiving various signals with the exception of speed, information from the three height sensors, and the air suspension service switch. For additional information about UBP, refer to Section 418-00 .
The 4WAS system holds vehicle height when any door or rear hatch is opened. The system stores front and rear vehicle height the moment any door is detected open. The system then maintains this height regardless of the addition or removal of a load. The system returns to its commanded height when all doors are closed or vehicle speed exceeds 24 km/h (15 mph).


Vehicle Height Modes Ignition State Transfer Case Mode Speed or Speed Range Resulting Vehicle Height OFF 4x2, A4WD, 4x4 HI N/A Kneel (TRIM - 25 mm) ON and RUN 4x2, A4WD, 4x4 HI All speeds TRIM ON and RUN 4x4 Low Below 40 km/h (25 mph) Off-Road (TRIM + 25 mm) ON and RUN 4x4 Low Above 40 km/h (25 mph) TRIM OFF 4x4 Low N/A Stays at current position (prior to ignition transition)
Air Suspension Service Switch
The air suspension service switch signal is needed to wake up the 4WAS module. Without the module receiving this signal, the 4WAS system is inoperative at speeds below 24 km/h (15 mph) and will not react when the vehicle is raised or lowered. At speeds above 24 km/h (15 mph), the system will be active as if the air suspension service switch is in the ON position.
Vehicles without message center When the air suspension service switch is in the OFF position and the ignition switch is in the RUN position, a "CHECK SUSP" will appear in the RH corner of the instrument cluster.
Vehicles with message center When the air suspension service switch is in the OFF position and the ignition switch is in the RUN position, the message center will display "SUSPENSION SWITCHED OFF"
Air Compressor
The air compressor:
  • consists of the compressor and vent solenoid; neither are replaceable as individual items.
  • is a single cylinder electric motor driven unit that provides pressurized air as required.
  • is powered by a solid state relay, which is controlled by the 4WAS module.
  • passes pressurized air through the compressor air drier that contains silica gel (a drying agent). Moisture is then removed from the compressor air drier when vented air passes out of the system during vent operation.
  • has a single port drier that can be replaced separately.
The vent solenoid:
  • allows air to escape from the system during venting actions.
  • is part of the air compressor cylinder head.
  • shares a common electrical connector with the air compressor motor.
  • is enclosed in the cylinder head casting, which forms an integral valve housing that allows the valve tip to enter the pressurized side of the system.
  • has an O-ring seal that prevents air leakage past the valve tip.
  • opens when the 4WAS module determines that lowering is required.
  • provides an escape route for pressurized air when system pressures exceed safe operating levels.
  • has a 1034 kPa (150 psi) internal relief valve.
  • is installed with the air compressor as a unit.
Air Spring
The 4WAS system has front and rear air springs. The air springs provide a varying spring rate proportional to the system's air pressure and volume. The air suspension system regulates the air pressure in each air spring by compressing and venting the system's air. Increasing air pressure (compressing) raises the vehicle; decreasing air pressure (venting) lowers the vehicle. Vehicle height is maintained by the addition and removal of air in each air spring through an air spring solenoid installed in the upper spring cap and energized through the 4WAS module command.
Air Lines and Fittings
NOTE: Apply a soapy water solution to the air lines to verify the location of air leaks. If the air lines are cut, ruptured or leaking, a service repair kit is available.
Nylon air lines with quick connect fittings connect to the air compressor and air spring solenoids. The compressor assembly output line is divided by the use of a fitting to supply the front and rear air springs. Fittings are also used to divide the air supply to the RH and LH air spring solenoids.
Air Suspension Height Sensors
There are two sensors used for the front suspension and one sensor used for the rear suspension. The sensors send a voltage signal to the 4WAS module. The output ranges from approximately 4.50 volts at minimum height (when the vehicle is low or in full jounce) to 0.50 volt at maximum height (when the vehicle is high or in full rebound). The sensors have a usable range of ± 45° compared to total suspension travel of 196 mm (7.84 in) at the front wheels and 240 mm (9.6 in) at the rear wheels. Therefore, the sensors are mounted to the suspension at a point where full suspension travel at the wheel is relative to the travel at the height sensor. The front height sensors are mounted to the frame and the links are attached to the upper arm ball studs. The rear height sensor is mounted to the frame and the link is attached to the rear lower arm ball stud.
When the height sensor indicates that the vehicle is lower than trim under normal driving conditions, the air compressor will turn on and pump compressed air to the system. When the sensor indicates that the vehicle is raised above trim under normal driving conditions, this will cause the air to be vented from the system to lower the vehicle to its trim height level.
Compressor Relay
A solid state relay is used in the air suspension system for compressor control. The relay incorporates a custom power metal oxide semi-conductor field effect transistor (MOSFET) and ceramic hybrid circuitry. The relay switches high current loads in response to low power signals and is controlled by the logic of the 4WAS module.
The compressor solid state relay is energized by the 4WAS module to have high current flow from the battery to the compressor motor.
4-Wheel Air Suspension (4WAS) Module
NOTE: The 4WAS module must receive a ride height adjustment calibration and must pass a pneumatic test when it is installed new or swapped.
The 4-wheel air suspension (4WAS) module controls the air compressor motor (through a solid state relay), all air spring solenoids, and provides power to front and rear height sensors. The 4WAS module also controls vehicle height adjustments by monitoring the three height sensors and other universal bus protocol (UBP) signals. The 4WAS module conducts all fail-safe and diagnostic strategies, and contains self-test and communication software for testing the vehicle and related components.

Jan 06, 2009 | 2003 Lincoln Navigator

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