bgrabner

Got a problem I think is not unfamiliar to some of you, but I can't find via search a good answer to my problem. My '87 S4 constantly cycles one of its fans when the engine is warmed up - pretty loudly too. My coolant light is also always on when the car is running, but it does allow me to clear the "!" error light. I know my coolant level is good however, and the temperature guage is never higher than half, so i don't think I am in danger of overheating.

I know I ran across a writeup on a website somewhere that gave some ideas on how to troubleshoot this problem. It's more annoying than anything because the fan is pretty loud, but I am concerned about burning up the fan motor and having to replace it. Can anyone provide any ideas or suggestions on how to fix this, or where I can find more information on this topic? Thanks!

Bill

UKKid35

I thought the fans always worked in unison, are you sure the other works?

Robert_H

Bill,

I have an '89 S4 and one of my fans is pretty much on all the time as well. I received the HVAC troubleshooting document from Wally and have gone through most of the items.

It seems that when there is a problem with one of the fans, the output stage detects this and then instructs the other fan to take over, only at full speed. It goes on for about half a minute, shuts off and then go back on again. Once the temp gets to a certain level, this cycling starts.

The document states to check the fan operation itself by switching the connections between fans, but I have not had a chance to do this yet.

Perhaps Wally will chime in with his expertise on this. Good luck.

Rob

MikeN

Does the other fan ever come on??

Check both fuses #28 & #29.....each is for one of the fans. If fuses are good:

Turn on your A/C, both fans should come on to some degree, if only one comes on.....something is wrong. Check connection to fan that is not running......reseat if necessary.

With both fan and car off spin each fan blade by hand......notice any difference between the two??.......a common failure is the bearing to go in the fan motor......a difference you can feel by spinning the blades.

Swap fan motor connections.......if same fan doesn't move, bad motor.......if problem moves, then it could be the final output stage for the fans.

Dave H.

i had the same problem a couple years ago. ended up replacing the fan brain and the output stage. hasn't happened since...

bgrabner

Thanks for the reply's!

Question for Mike - any tips on how to swap the connections? I have only had my shark for a few months so I am still new to the engine bay..

Question for Dave - what is the fan brain - is that the same thing as a fan control unit? and what is the output stage? I am not familiar with that. Your suggestion may be the answer, I just want to make sure I understand the fix

Thanks!

MikeN

The cable for the fans runs down the passengers side of the fan shroud
in a groove and is held in place by little metal clips. As it travels down the shroud it splits in to two cables.....one for each fan. The connectors are of a simple "blade" type and can just be pulled off.......in other words straight down towards the bottom of the car. You should have enough slack in
each cable to reverse the connections. There is only one way the connectors can go on to the motors, so don't force anything and if it doesn't seem to fit turn the connector around and try again. If the same
motor still does not work......then I would be about 99.9% sure it was the motor that was bad. If the other fan stops working then the problem is
with the final output stage, fuse, etc......