Checked the signal coming from the black wire on the fan with an oscilloscope and found it very eratic. It is showing a square wave PWM signal but it was between 3-5volts while the fan was turning and when it was stoped it was all over the place .44V to 2V.

I also have another spare new fan here that I plugged in and it did the same thing, stops after about 10secs.

Does anybody know where the signal comes from? or have and schematics.

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2006 X5 3.0d...