BMW E36 Blog

Electric Fan Problems On My BMW E36

20th April 2008

Electric Fan Problems On My BMW E36


I’m having 3 problems with the electric fan in my car.

First, I know that the electric fan should have 2 speeds: Low and High. My electric fan does work on the high speed only, I guess that I’m having a problem here. I also noticed yesterday that the temperature gauge moved a little bit towards the one clock instead of the normal 12 clock position when I left the engine running (with the A/C on) and went to grab something. The second problem that I have with the fan is that whenever the fan kicks in, the RPM bounces for like 20 seconds or a little bit more, then it returns to normal.

The third problem happens usually after I reach home and turn my engine off, the electric fan kicks in and keeps working for like 30 or maybe 40 seconds before it stops.

I noticed these problems before (except for the temp. gauge one) but I didn’t pay much attention to it until yesterday when I popped up the hood and decided to trace how the electric fan is supposed to work. The task is simple; there’s a coolant sensor that is placed in the returning hose to the car’s radiator. This sensor is supposed to keep watching the temperature of the coolant and to send a signal whenever the coolant temperature exceeds a certain value (176F, 80 C according to Bentley Manual).

To my surprise, I found that the electric fan power source is not connected to any special part that is connected to the ECM as I previously thought!! Instead, it’s connected to a relay that can connect/disconnect the fan with the battery directly LOL! I have to say that the electrician who used to work on my babe is a stupid one 😀 . The relay of course is controlled by the coolant sensor and whenever the coolant reaches a specific temperature, it will simply give the relay a signal and thus closes the electric fan circuit with the battery which drops the power from the battery because as we all know, the fan consumes a lot of power and thus the RPM starts bouncing because the ECM is trying to compensate for the loss.

So, I’m trying now to figure out how to re-connect my electric fan correctly to the auxiliary fan relay (which I found in the BMW E36 fuse box layout).

Anyone of you guys can help with this? I need to know what are the colors of the wires that are connected to the electric fan and to the coolant temperature sensor. Some pictures may be good too 😉


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posted in Cooling System, Technical Info, Tips & Tricks, Uncategorized | 5 Comments