Dino D., I have read the comments about the early 6 cylinder cars having the wiring for the Aux fan "wrong", I am not convinced that the wiring is "wrong" in my opinion the wiring is in fact as intended by BMW. The fan switch in the radiator has settings for 90/99c, I believe that BMW intended the "Low" speed on the Aux fan for cooling with the A/C on (not controlled by the fan switch) and the 90c switch point to be for "High" speed for overheat protection. I think the 99c setting is redundant and effectively not used (economy of scale on fan switch's), having the Aux fan High speed coming on at 99c would not provide a whole lot of "Overheat protecion". On my 97 2.8 the Aux fan comes on low when the A/C is switched on and on high if the temperature gets to the 90c. I am planning on replacing the mechanical fan with a Spal electric fan controlled by a M44 (80/88c) fan switch, using the 80c setting to control the Spal fan and the 88c setting to control high speed on the Aux fan. The car will be used in South Florida for most of the year, so overheat protection is justified.
The Aux fan on mine never kicked in on low or high speed due to coolant temp. It only worked with the aircon on. Even when the car got over 90c it never kicked in.
Unlike yours which seems to be wired correctly.
Now I’ve changed the wiring it works like yours - if it was t the wiring, why didn’t mine work? The only change I made was the wiring!
I only discovered this from another forum, I think US. I wasn’t the first but it seems only very early cars were affected so not very common.
Mine certainly was and once rectified the car worked just fine with only the Aux fan (no viscous).
what year is yours? Is it a 2.8 or 2.5/2.0?
the info I came across only refers to early 2.8’s - I don’t know about other 6cyl models.
