Electric cooling fan help

[Adam f]

2005 Liberty 3.7 automatic. Radiator fan comes on but only runs for 3 seconds, then ***** off for 10 seconds, then comes back on for 3. Never stays on. As a result, the a/c overheats and gets warm. I disconnected the coolant temperature switch on the manifold, and the fan turns on high and stays on. I swapped relays around with the blower motor relay and it still kicks on and off. I replaced the coolant temp sensor and still kicks on and off. I don't know where to go from here. I'm thinking ECU? Is that what controls when and how long to turn the fan on and off?

 

[uss2defiant]

The e-rad fan only comes on at certain conditions.

OPERATION
The electric radiator cooling fan is controlled by the Powertrain Control Module (PCM) through the radiator cooling fan relay. The PCM regulates fan operation based on input from the engine coolant temperature sensor, battery temperature sensor,air
conditioning select switch and vehicle speed. The fan is not energized during engine cranking regardless of the electrical input from the temperature sensors and ,air conditioning switch. However, if engine operation conditions warrant fan engagement, the fan will run once engine starts.

Vehicles Equipped with AC:
In addition to using coolant temperature and battery temperature sensor to control cooling fan operation, the cooling fan will also be engaged when the ,air conditioning system is activated. The relay is also energized when, air conditioning is selected and coolant temperature is above 95° C ( 203° F), or , air conditioning is selected and battery temperature sensor is above 41° C (106°F). It will then de-energize when , air conditioning is selected and coolant temperature is below 92° C (198° F), or , air conditioning is selected and battery temperature is below 38° C (100° F).


Here are some questions:
1. does it come on when the AC is on? Note that there are certain temperature conditions as well even with the AC being on.
2. Any CEL codes?

 

[uss2defiant]

the pcm sends a pwm contol signal to the radiator fan relay. it is located on the driver side.

tjkj2000's pic

You must be registered for see images attach

 

[Adam f]

Thanks for the help. Fan starts and stops like described with the a/c on. Haven't tried without a/c.

Replaced temp sensor on manifold behind alternator and did not change anything.

fan relays on this 2005 are located in the fuse box under the hood. I swapped them around with the blower motor relay and no change.

Pretty sure the pcm is bad.

 

[uss2defiant]

Is your 2005 with the dual speed e-rad fan?

When your AC gets hot like you mentioned, is your AC compressor still engaged?
Maybe the fan is turning on and off as your compressor is being engaged on and off.
Your refrigerant still up to pressure?

 

[Adam f]

I guess its dual speed, not sure. It only comes on for 3 seconds and shuts off.

A/C compressor is running while the fan cycles. Fan never comes on with A/C turned off. (I don't think, haven't fully tested this) Starts off cool, low side PSI is around 30-40. Sit there for a minute and pressures start to spike, air gets warm, compressor begins to cycle on and off due to high pressure, and air in the Jeep is hot. Unplug the coolant sensor, fan comes on full time, A/C pressures begin to drop back down to 30-35, A/c is cold in Jeep, all is good.

Drove it around for 30 minutes and then parked at idle for 10 minutes with the sensor unplugged and fan running, air is ice cold, all is good. Plug sensor back in, fans shut off, begin to do cycle, A/C pressures spike, starts blowing warm.

 

[uss2defiant]

hmmm.... I'll have to read around the 05 FSM
on the meantime here's a link to it
Index of /manuals/Jeep/KJ

From a quick look, your KJ does have the dual speed fan with 2 separate relays controlled by the PCM. both relays are in the power distribution center.

 

[Adam f]

It was driven over the weekend with the sensor unplugged. Hard to start when cold, but OK when warm.

I plugged it in, and now it seems the high speed fan isn't working at all. The fan cycling has stopped completely. I let it run for 5 minutes or so and then what I assume is the low speed fan kicked on at abot 230 and then kicked off at about 210. It did this a few times, with a/c on and a/c off.

So, I don't know what the heck is going on now. Seems high speed is dead?

 

[uss2defiant]

did you replace it with a MOPAR cololant temperature sensor?

Can you try supply +12V to radiator fan connect pin 1 and then later to pin 3?
Pin 1 is the low speed and pin 3 is the high speed. Just to see whether there's anything wrong with the e-rad fan.

 

[Adam f]

Replaced it with a Standard Motors part.

I will try putting power directly to the fan. Which pins are which on the connector?

 

[uss2defiant]

usually, try to replace electronic components w/ MOPAR.

There's a 3 pin connect to your fan.

You must be registered for see images

Can you try supply +12V to radiator fan connect pin 1 and then later to pin 3?
Pin 1 is the low speed and pin 3 is the high speed. Just to see whether there's anything wrong with the e-rad fan.