Been searching on the board for something similar - no success...

Picture this situation: I start the engine and let it warm up for three to four minutes. The engine is then more or less 'operational'.
I start driving (nice and slowly), but as soon as I slack off on the throttle (eg. when approaching a red light) the fan comes on... And the engine is definetely not overheating at this time - the water in the radiator is still cold...

It seems a bit weird that this fan should come on when the engine is basically ice cold?
AC and heater system otherwise works perfectly so I would assume that there is a problem with the way the blower is controlled (temperature switches or similar).

Any suggestions?


Thanks in advance

Michael Handreck
'93 GTS Polar Silber Metallic

 

It sounds like you have something amiss with the fan control system. The fans are supposed to come on when: the AC is turned on, or when one or more sensors tell the system "the engine is hot". There are four sensors. From front to back they are: The radiator sensor (BTW, if this one is not pushed in properly the fans will come on all the time), the water AC pressure or temp sensor (located on the receiver/dryer), the hood open sensor (shuts off a fan when the hood is open, but will not if the temps are too high), and the intake manifold temp sensor (located at the top of the intake manifold). Other items to check are the fan control unit (in the bolster next to the passenger seat) and the Final Output Stage [FOS](the finned black box next to the hood lock).

The procedures to check all these items is well covered in the Service Manual. When my system was acting funny, I was able to figure out that the FOS was the culprit.

Good luck.