Hello and Interesting Aux Fan Question

[rycar550]

Hi, I am new to the forum.  I recently acquired a 1991 318i and love it so far.  I have an interesting Aux Fan problem that I can not seem to figure out.  The minute I start the car, regardless if the A/C is on, the Aux Fan comes on at HIGH Speed.  Having said that, I know that the fan should not come on unless the A/C is on or the car gets very hot.  I thought at first it could be the low speed resistor, but now I am not so sure.  I thought that if the resistor was bad, the fan would not come on unless the engine temp was high, and then it would come on at high speed.  Am I right? So to recap, the aux fan is on high and all times and not sure why!  Can anyone help??

Ryan

[D. Clay]

The only time it should be on high is when the high speed temp side of the sensor in the radiator is activated. The A/C only runs the fan on low period. I would suspect a shorted temp sensor in the radiator. Pull the plug out and check continuity with the motor cold. Both high and low speed sides should be dead.