clancy

I am trying to determine whether I have a bad coolant fan control thermal switch #8d0959481b or if it is the fan control module #8d0959501d.

My understanding is that if the thermal switch (the one on the lower radiator hose) is bad then the switch defaults and the fans are always on. This is not my situation. Mine is both electric fans are off unless I turn on the air conditioning or the coolant temperature requires. But they do not appear to ever go to the high speed.

Is this always the case? If no high speed then it is always the fan control module? I am not getting any DTCs. Is there a way to check the high speed function of the fans with a Ross VCDC?

Thanks

clancy

Any suggestions here? I have read lots of archived discussions. Some say if the fans work at all then it is not the thermal switch. Others say they changed this and solved the problem. Others say the faulty fan control module threw a DTC. Is this always the case? I am hesitant to just throw parts at this.

johnkk

You may have nothing wrong. The only time my electric fans run is when the A/C is on. Years ago, I had the rubber seal stuck in the fan issue and it burned out the control module. Then the fans default to ultra high speed (jet turbine sound). Once the module was replaced and the seal yanked out, the engine has never gotten hot enough with A/C off to trigger the fans. With A/C on the fans run at what I would call a low/mdedium speed. I suppose if you idled the car for a long time on a hot day with the A/C on, they would eventually run faster. Give it a try.

re VCDS. There is a HVAC test section, but not sure if the sensors and control modules are monitored. (not hooked up to car now, so can't drill down past top tier of VCDS).

N_Jay

Interesting, my electric fan is loud whenever the AC is on.

Wonder if my control module is cooked?

clancy

Thanks for the feedback. I have noticed that the coolant temp gauge occasionally rises above the midway point on hot days (80+) when the AC in on and I am either idling in traffic or on a long climb at speed, 60+ mph.

As the thermal switch is a minor pain to replace I did not want to do this if it was known to not be a potential repair. Certainly easier and cheaper than the fan control module but still... I'd prefer to just replace the appropriate part if it can be identified first.

clancy

Went through all the options on Ross VCDS and did not find any codes for only low speed only on fans. Nor did I find an option to test the fan high speed operation.

Guess I will first replace the temp switch hoping it fixes the high speed operation. Then proceed to the fan control module if necessary.

UncleScar

I don't think you have anything to worry about "high" speed only happen when A/C on. Keep an eye on both temp. Levels. My 4.2 has a clutch fan plus 2 electric. I thought the same. There's a write up on how to test FCM and the TTS. I live in Florida and my fans only go high with A/C. and yes it can be scanned. Well atleast that there's a fault that you can check. Search the forum, I seen the write up when I thought I had a problem. Depending on mileage I would aim for TEMP tensor. Coolant is corrosive and causes scale, so sensor will fail. FCM would fail if you got it super wet or it got damadged since its in a bad location.

clancy

My issue is the temp gauge goes above mid point when idling in traffic on hot days with the AC on, or when climbing long hills at higher speeds on hot days with the AC on.

My understanding is even if I test the high speed operation by jumpering the temp switch per the write up this does not verify the function of the fan control module. I also understand the FCM is a common failure, but do not wish to replace it unless I can confirm it is bad.

Thus far I have only had the car begin to overheat a couple times. No codes have been set. Do I just wait until it gets worse? Or can I verify what the problem is prior to an overheat?

johnkk

Yup, if sounds like a jet turbine. module PITA to replace. nuts/bolts very hard to reach without pulling bumper. Now that I am familiar with bumper removal, that's the easier way.

Look for loose rubber strip under fan behind radiator. yank it out. Unneeded vestigial body part. They jam the fan and the module burns out.

jseklund

I've had this same issue for 2 years. When I get caught in traffic the temperature rises above the mid point and the A/C cuts out. The engine is sufficiently air cooled when the car is running and everything is fine. But when the air flow drops, the electric fan is needed and it doesn't turn on. I put a 12V battery to the fan directly, and it didn't turn on, so I know my fan is dead at the very least....but it hasn't been enough of an issue for me to spend the time & money to fix it....