2003 grand marque excessive bouncing on highway. may be caused by automatic leveling air bag. can you run safely with air switch turned off?

Which heating / a/c system does it have manual or automatic ?

System Air Flow Description - Manual Climate Control
System Airflow Description - EATC - Electronic Automatic Temperature Control

It would take some rewiring since everything is set to work automatically and designed to level the back end of the car. The doorjam switches are built into this system and the height adjuster is mounted to the underframe.

You might be able to use an air-shock pump and disconnect the Factory unit. The support bags would then work off of a switch you would install. Can't say if bags would respond quick enough to do what you want. THE BAGS CAN NOT BE WITHOUT PRESSURE, because you have no springs. Basically not impossible but probably not a good idea.

You need to find out what the fault code is. It will direct you to the area responsible.

Air Bag Diagnostic Monitor
WARNING: UNDER NO CIRCUMSTANCES SUBSTITUTE ANOTHER FUSE VALUE FOR THE 10A BATTERY FUSE. ANY FUSE OTHER THAN 10A MAY CAUSE DISARMING FAILURE AND MAY RESULT IN DANGER TO THE OCCUPANTS OF THE VEHICLE. DO NOT ATTEMPT TO REPLACE THE 10A BATTERY FUSE UNTIL THE AIR BAG SYSTEM FIRST HAS BEEN DEACTIVATED (SEE DEACTIVATION PROCEDURE FOR DETAILS).
NOTE: The safing sensor is internal to the air bag diagnostic monitor (14B056) and is not replaced separately.
The air bag diagnostic monitor continually monitors all supplemental air bag restraint system (SRS) components and wiring connections for possible faults in the system. If the air bag diagnostic monitor detects a fault in the SRS when the ignition switch (11572) is in the RUN position, a diagnostic trouble code (DTC) will be displayed by the air bag indicator, located on the instrument cluster (10849).
The air bag diagnostic monitor does not deploy the air bag in the event of a collision. The LH or RH air bag sensor and the safing sensor determine when to deploy the air bag.
The air bag diagnostic monitor illuminates the air bag indicator for approximately six seconds when the ignition switch is in the RUN position and then turns the indicator off. This shows that the air bag indicator is operational. If the air bag indicator does not illuminate or the indicator stays on or flashes at any time, a fault has been detected by the air bag diagnostic monitor.
DTCs may not be displayed for approximately 30 seconds after the ignition switch is placed in the RUN position. This is the amount of time the air bag diagnostic monitor requires to perform all tests and verify system faults.
Each DTC (a series of flashes and pauses of the air bag indicator):

• Represents a two-digit number.
• Is always displayed at least twice.

If the diagnostic monitor detects a fault in the air bag system, a DTC will be written to the diagnostic monitors non-volatile RAM (NVRAM). This DTC will then cause the lamp to flash a lamp fault code (LFC) on the air bag indicator and can be retrieved with the New Generation STAR (NGS) Tester. After repair, the DTC may then be cleared from the NVRAM.
If a system fault is present and the air bag indicator is malfunctioning, an audible tone will be heard. The tone is a series of five sets of five beeps. If the tone is heard, the air bag system requires repair.
If a fault exists that makes unwanted air bag deployment possible, the air bag diagnostic monitor will attempt to remove deployment power by turning on a solid state switch to blow the 10A battery fuse 2.
If the 10A battery fuse has successfully been blown by the air bag diagnostic monitor, the air bag diagnostic monitor will not attempt to blow it again until the proper fault has been repaired and cleared (see Diagnostic Trouble Code Clearing procedures for details). The air bag diagnostic monitor will store both the unwanted deployment DTC and the loss of deployment power DTC. The loss of deployment power DTC is the highest priority.
DTCs are prioritized numerically. If two or more faults occur at the same time, the fault having the highest priority will be displayed first. After that fault has been corrected, the next highest priority fault will be displayed.
The air bag diagnostic monitor includes an internal backup power supply. This feature provides sufficient backup power to deploy the air bag in the event the battery (10655) or battery cables are damaged in a collision before safing and air bag sensors close. The backup power supply will deplete its stored energy approximately one minute after the positive battery cable is disconnected.
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The DTCs can be retrieved with New Generation STAR (NGS) Tester using the Retrieve/Clear Continuous DTCs option. Any DTCs stored in the air bag diagnostic monitor will be displayed on the NGS along with a brief description of the DTC. If no DTCs are present, the NGS Tester will display a SYSTEM PASSED message. This option can also be used to clear DTCs from the air bag diagnostic monitor memory, as long as the concern no longer exists. Once a DTC is logged into the air bag diagnostic monitor memory, it will stay in memory until 255 key cycles have been recorded or until the NGS is used to erase the DTCs. Once 256 key cycles have been recorded since the concern was last detected, the DTC will automatically be removed from memory.

means eithor you have a bad air bag sensor or the air bag is defective or you have a switch and turned off the air bag becareful not to deploy the air bag

if the vehicle is sagging or bottoming out on bumps and potholes it's time to replace springs. if vehicle bounces and has excessive sway then the shocks (struts) are bad.

You only need to disconnect negative battery cable to make it safe to work on.

Take a volt meter and put the test leads on the battery terminals,
red to positive,
black to negative,
set meter to 12 volts dc
If the meter reads less than 14 to 15 volts dc, the alternator is not charging and needs a new one.

Sounds like your alternator is giving a weak charge. You can have your alternator tested at your local parts store.

First, you should have a warning light telling you it is not working. There is a switch for the air suspension underneath the glovebox-right hand side or in the rear hatch area on the left panel..make sure it's on. If all 4 air bags are deflated it could mean the air pump or actuator is malfunctioning.

Sounds like it needs more air in bags. Add air and squirt really soapy water over bags and attached lines to find leak. May have to replace bag/bags or feed line from pump. I would think it would be a feed line if car stays up with switch off.