94 C280 Auxillary fan always on

[H.Hamid]

I have 1994 C280 European made. The two auxiliary fans are always on even after I turn the ignition on and before starting and running the engine. And the ECT gauge B13 is not working at all. I have checked the wiring from the sensor all the way to the instrument panel and there is no shortage.


The followings are the kind of tests I have done on this car.

As soon as I turn the ignition on the fans go on.

I took the relay K9/1(15Amp) out the fans run on hi speed.
I took the relay K10 (30Amp) out the fans run on low speed.
I took the relay K9/1 out and unplugged the ECT sensor (A/C) B10/8 the fans run on hi speed.

I took the relay K9/1 out and I shorted the ECT sensor (A/C) B10/8 the fans run on hi speed.

I grounded Blue-Red wire of Refrigerant pressure sensor the fans stops for 3 seconds and then comes back on regardless of ECT sensor (A/C) B10/8 is connected or shorted or any combinations of fan relays are installed.

Temp gauge on instrument panel is not working at all.

I have run out the tests I knew. Please Help