After the engine has been running for 2-3 minutes, the cooling fans start operating quite frequently, way more than before. They also vary in turning speed. I can hear a relay clicking everytime they start spinning. They do it even with a cold engine. The temperature gauge behaves normally. It goes from cold to operating temperature and stays there without showing signs of overheating or overcooling.

Any idea? Faulty coolant temperature sensor? Where is it located?

Thanks.

Michel
89 S4 ROW
Canada

 

when they start remove one of the wires from the top of the intake sensor.
if they stop replace the sensor.
Please report back your findings

 

They indeed stop! Thanks!

This sensor has been replaced a year ago! Is it fragile or subject to break easily?

BTW: Do you get to fly the Mustang?

Michel

 

Okay, someone has to ask the obvious question...
You're not looking at the air conditioner fan are you ?

 

if the sensor got wet or was dropped or rough handled then it may have gotten damaged.

Note the S4 only has one set of fans they are on the back side of the radiator the earlier (86 and older had 2 fans one in front and one in the rear side of the radiator
One day i will be flying a Mustang, not now though

 

Similar problem now...

When the engine reaches its normal operating temperature, a hear a clicking relay, then the cooling fans start spinning, then they slow down without stopping for 3-4 seconds then the relay clicks again and the fans spool up again. It does it continuously until the engine is shut down.

Any idea? Faulty sensor? Which one? (The one on top of the intake manifold is disconnected)

Thanks.

Michel
89 928 S4

 

Mirousse, have you made sure that both fans are turning at the same speed? The clicking of the relay you are hearing is the test mode for the front flaps. If one of your fans is bad, the system will continually check to see if the system is operating properly.

 

One of our members here has a couple of hundred hours in them, Shrkbyte.

 

When the AC is on the fans run all the time.... (S4+)

Alan