BMW E36 Blog

Electric Fan Problems On My BMW E36

20th April 2008

Electric Fan Problems On My BMW E36

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

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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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There are currently 5 responses to “Electric Fan Problems On My BMW E36”

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  1. 1 On April 20th, 2008, Dennis said:


    Think my reley and sensor might be broken then, i have never ever heard my electric fan running,. Not even if i have been driving at 180 km/h for 5 hours, in 20 degree C sunshine…

    Think there is something broken, or does is my coolant just below 80 degrees all the time?


  2. 2 On April 21st, 2008, Tony Sticks said:

    Dennis, does your temperature gauge move beyond the 12 clock?

  3. 3 On April 21st, 2008, Dennis said:

    Hi Tony,

    No is does not move beyond 12 clock, sometimes when driving at high speeds (190- km/h) it stays between 12 and 13 clock. But it drops quickly to 12 clock again. I just think it’s weird i have never heard the electrical fan turn on, or is it just me being paranoid?


  4. 4 On April 22nd, 2008, Tony Sticks said:

    I’m not really sure. My car fan seems to be messed up, so I can’t judge about that. I suggest you take a look at your fan and how it’s connected. As long as your car’s temp doesn’t go up, I don’t think you have any problems.

  5. 5 On July 12th, 2008, sam said:

    just replaced my radiator in my 95 318i and now my temp stays at 12 for a while and then temp starts to rise slowly.even when i drive it begins to go past 12 after a electric fan also doesn’t come on at all even before i changed radiator the fan never came on and my temp gauge alway’s stayed at 12.could my problem be a fan relay,thermostat,water pump or more serious problem?