2002 Grand Cherokee Larado AC cooling fan (small fan in front of radiator fan) stuck and was running after car was switched off. I had to disconnect the battery to get it to stop running. When I tried to...
IT DONT WORK THAT WHY. (on/off)
NO ENGINE STATED, SO on exact answers. 4.0L or 4.7L ???
The engine cooling and HVAC rules govern this (computer tables and logic)
the service manual cover that,
did you SCAN the PCM at the failure then scan it again after, no?
did you know some cars run the fans parked to prevent overheat soak damage to the engine and trans? all have hood sticker warning telling you to stay way from fans, , until fully cooled engine or pull battery neg lug for safety. just saying that so you are safe fiddling all cars.
the fan(s) run via truth tables, logic (computer)
if cold outside why run a fan?, and waste fuel and cause green house gasses for fun. or make noise for fun, answer it doesn't.
it runs the fan ONLY when needed, is the answser
and is very complex, the newer the jeep gets.
On most cars even as old as 1995 , the condensor fan control would stay off if ambient temps are below 50f. this is not new logic.
Chapter 24 covers HVAC. in The service manual SM.
not only that, you failed to test the AC per the SM and failed to scan the PCM to see if there are HVAC faults. causing this fan disablement's. on purpose.
this car come with 2 type HVAC, manual and ATZ (climate control fancy) the rules for each are not the same (potentially)
the PCM controls the radiator fan on the 4.0L with a relay.
so is 100% pure (ATZ/BCM/PCM) logic doing that.
the 4.7L has hydraulic motor powered engine cooling fan
as you many not know the A/C condensor rams hot AIR
to the front of the engine RAD and cause it to overheat
so the engine fan is very much part of this regulation system.
The AC will also shut down for many AC related errors
and will do so if the engine or transmission over heats.
there are 3 , 4.0L systems, for fan control
clutch fan or electric and one has a PWM modulated fan control module (its a transistor not relay in this case)
her is what chapter 7 states
PWM FAN CONTROL MODULE -
The pulse width modulated (PWM) radiator cooling
fan relay is located behind the front bumper fascia
below the right headlamp.
The PWM relay is used to control the speed of the
electric radiator cooling fan. It allows for multiple fan
speeds. This allows for improved fan noise and A/C
performance, better engine cooling, and additional
PWM relay operation is controlled by the Powertrain
Control Module (PCM). To operate the PWM
relay, the PCM looks at inputs from:
† Engine coolant temperature
† Ambient temperature from the body controller
† Vehicle speed
† Transmission oil temperature
† A/C switch position (A/C request)
the SM does not list all rule and tests for this device.
here more quotes from your missing book
If an open or shorted condition has developed in
the relay circuit controlling the electric radiator fan
or fan control solenoid circuit controling the hydraulic
fan, a Diagnostic Trouble Code (DTC) can be set.
If the problem is sensed in a monitored circuit
often enough to indicated an actual problem, a DTC
is stored. The DTC will be stored in the PCM memory
for eventual display to the service technician.
fans stuck on quotes
1. Fan control sensors inoperative.
1. Check for DTC's. Verify sensor readings.
2. Fan control solenoid stuck 9on9. 2. Check fan operation speeds. Refer to fan
speed operation table.
3. Fan control solenoid harness
3. Check for DTC 1499. Repair as required.
4. Transmission temperature too high.
4. Check for transmission over temp. DTC.
5. Engine coolant temperature too high.
5. (a) Check coolant level. Correct level as required.
(b) Thermostat stuck. Replace thermostat.
(c) Water pump failed. Replace water pump.
(d) Coolant flow restricted. Clean radiator.
(e) Air flow over radiator obstructed.Remove
the 4.7 liter engine the fan speed is base on above
and says, A/C system pressures.
the 4.7 then can can run at 500 rpm even when OFF. (SM)
now how to test the fan.
get engine hot, (drive 10miles say)
then park, and lest engine idle until the engine overheats
it will (but not in alaska, dig?)
and then the fans come on at bout 225f .. (about this is ball park)
if using a 4.7L say so, its totally DIFFERENT
Mar 15, 2017 |
2002 Jeep Grand Cherokee