So my coolant light is ON, ac only working when driving, radiator fan won't kick in. I checked the 50 AMP fuse and its good. The fan works when hard wired to the battery. I am thinking that the fan relay, the black box with the fan wiring coming out of it might be the problem, part number A 025 545 59 32. I took it out but don't know how to test it if its working. Any ideas?

 

Check for 0-12VDC while the car is running? I think it's a variable-speed drive.

 

There is no power coming out. Otherwise the fan would tun on. I was thinking that the thermostat might be bad.

 

Look in the Repair Manual, I'm sure that there is a procedure to check the item out.

 

The thermostat does not control the fan, it only controls the flow of coolant.

The Fan Control Module (FCM) is not a relay, it is a control module and it provides Pulse Width Modulated 12 volts to the fan motor.
It also produces pulses in response to the pulses sent to it by the ECM. Your coolant light is on because the ECM is not getting pulses back from the FCM. This is because your FCM is bad!

How it all works: The ECM actually determines the fan speed needed in response to the temperature sense the ECM is getting from the coolant temperature sensor and tells the FCM what speed to run the fan at. When you turn the A/C on, the ECM tells the FCM to at least run at slow speed so you have air movement over the condensor when stopped. If the engine temperature is high, the fan will run at higher speed, no matter if the A/C is on or not.

Since the FCM is not turning the fan on, you have no air movement over the condenser when stopped so you have no A/C when stopped.

Consider:
1) You have proven the fan motor is good.
2) The ECM is lighting the "Coolant Light" (many things can cause that light to come on, but ONE is that the ECM has lost communication with the Fan Control Module).


I am not there, but it certainly seems certain that the Fan Control Module is bad. I think you are safe in ordering a new FCM. It is POSSIBLE that the ECM is bad, but if it was so screwed up that it can't talk to the FCM, why is it still smart enough to light the light and run the car?

Get ya a new FCM.

Yer welcome.

 

Won't do him/her any good. The procedure is to connect the diagnostic thingy and command the fan to come on. I BELIEVE the tool also has a communication test to the FCM, but again, without that many-thousands-of-dollar tool, the only other way to confirm it is to trade FCM's between cars.

Good reason to have two Crossfires. You could loan them your FCM , since it is still winter where you are.

 

Thanks guys. I ordered the FCM and a new thermostat just in case. We'll see what happens. And when I think that I went through two summers with no AC. The engine temp never ran high and the coolant light came on only recently.

 

1. Well that's not quite true, after step one, which has the DRBIII simulating the BCM I believe, you go to step two etc and these test for volts and amps.
   
2. The DRBIII checks the BCM and if that's OK you get the multimeter out.

 

Yea, I didn't look it up Dave, I was at work. But I did remember thinking that you didnt get very far without the DRBy thing.