:help My Auxilary fan on my 1982 528e is not working and will cause the car to overheat during stop and go driving. For the time being I have used a paper clip to jumper the two wires to the radiator fan switch which will allow the fan to run but it runs anytime the key is turned on and this has caused the fuse holder to overheat and melt to the point the fuse loses contact.

Question is do I need to replace the Auxilary fan resistor or is it the radiator fan switch that is bad?

Thanks

Ok, I'm stumped... I replaced the resistor and I know the resistor is working as when I turn the key on and push in the A/C button, the fan comes on, although at low speed, not sure if that is right or not as when I use a paper clip to jumper the radiator fan switch it runs much faster.

Upon starting the engine I ran the A/C for a while and the fuses were getting hot and started smoking. I turned off the A/C and they stopped smoking.

I then ran the engine up to operating temperature without the A/C on and the Auxillary fan never turned on. The engine just started over heating.

I also replaced the radiator fan switch with a brand new 99 degree switch, only one available at the auto parts store, and still no luck. I then replaced it with a used 91 degree switch and again no luck.

What else could it be if not the Radiator fan switch or Auxillary fan resistor?

Ok, I finally fixed the problem. I replaced the thermostat even though the hose was getting warm, this was the only thing I hadn't replaced yet.

The resistor had been bad so that was part of the problem but also the fan finally comes on at low speed when the temperature needle on the gages is about an 1/8" away from the red zone. A little bit later the high speed kicks on so I now know that both my fan switches work.

One thing I will change and anyone else that has this problem might consider is getting a lower temp switch. The stock 91 and 99 in my opinion take too long before they kick in and start the fan. Instead I'm going to order a 82 degree switch for the low speed and use the 91 degree switch (previously the low speed switch) in place of the high speed. This requires changing the terminals as they are smaller.

Car is now good to go and driving down the road.