Electric Rad Fan will not run

[Brendan]

My electric rad fan will not come on, I have tested the following:

swapped the Relay with another (has about 4 or 5 of the same relays for fan) still did not come on
checked 60 amp fuse with meter.... good
Hooked the fan directly to the batter both hi and low engage the fan

I know it could be the engine temp sensor, have not replaced yet, but i do have a programmed PCM coming because i figure i ma down to either the PCM or the temp sensor. The reason for the PCM is I have other issues like constant multiple misfires and crank/cam shaft errors.

My question is if i turn the AC on should the Rad Fan come on regardless of the temp?
I read some say it should and others say no its temp that triggers it on.
If it doesn't come on cold after turning the AC on is there a way to test the temp sensor with out replacing?
I can run it until it over heats and still don't get an error on the bluedriver about temp or the fan. but did get one a long time ago while trying to diagnose the misfires showing fan error.

I have a week until the PCM arrives so looking check a few other possibilities off the list


2008 Jeep Liberty
3.7L
79,000 KM

 

[lfhoward]

Yes, turning on your AC should always kick the electric fan on.

 

[LibertyFlip]

These are the two threads that I referenced when trying to diagnose my temperature sensor/fan operation - I have seen statements that say otherwise, so no promises that this is 100% correct factory information:

https://www.jeepkj.com/threads/help-fan-relay.57994/
Post #2 here from uss2defiant

https://www.jeepkj.com/threads/adding-a-true-water-temperature-gauge.63811/
Post #15 here from LibertyTC

I'm not familiar with BlueDriver specifically, but after browsing their site it looks like you should be able to access the live data of the coolant temperature reading - that's where I would start. If you think that it's off (that was my problem) you can check the temperature at the sensor with a laser thermometer (make sure it's pointing straight up and down, don't do it at an angle).

If all else fails, these sensors send an ohm reading. I have an OEM one and a Stant one laying around that I haven't had a chance to compare yet. That would be the way to see exactly what the sensor is reading, but I would think the computer reading from your scanner should do the trick

 

[Brendan]

Great Info thanks, gives a few things to try until the PCM shows up.

One question on the PCM if its programmed to my VIN do i need to program the cranksshaft/firing order before/after swapping pout the PCM? read somewhere about having to reprogram this after replacing PCM .

 

[uss2defiant]

my info is from FSM. The KJ FSM is freely accessible and anyone can get to the FSM themselves and read the info.
Do note that I am only mostly familiar w/ the 02 and 03.

 

[Ksat]

How would you test to see if the fan comes on without actually making the car run hot?

 

[Brendan]

Like my original question was that..... if i turn the AC on whether the jeep is hot or not should the electric fan come on . I believe the answer above was yes. i was confused becasue i haev heard yes and no on that question.

 

[uss2defiant]

here's the link to the 08 FSM brought to you by Tim


https://www.jeepkj.com/threads/factory-service-manual-links-kk.74533/#post-770465

 

[uss2defiant]

copy and pasted the info from the 2008 FSM for you.

OPERATION The electric radiator cooling fan is controlled by the Powertrain Control Module (PCM) through the radiator cooling fan relays. 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.

On vehicles NOT equipped with AC: The relay is energized when the coolant temperature is above 80° C (176° F), or battery temperature sensor above -12° C (10° F). It will then de-energize when coolant temperature drops below 82° C (180° F), or battery temperature sensor below -9° C (16° F).

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 deenergize 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).

 

[uss2defiant]

Like my original question was that..... if i turn the AC on whether the jeep is hot or not should the electric fan come on . I believe the answer above was yes. i was confused becasue i haev heard yes and no on that question.

Yes, the e-rad fan will engage when the air conditioning system is activated but it will then deenergize 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).

 

[Brendan]

Any idea how long the fan will stay engaged (spinning) when cold, example is a few minutes or just seconds ?

 

[uss2defiant]

Fan should engage until the deenergize conditions are met.
There's no time limit stated in the FSM.

I think you should read the FSM....