Aux fan troubleshooting - solved

[SharkGill]

My aux fan does not run at all. I've followed this guide http://www.nmia.com/~dgnrg/page_20.htm the ballast resistor and fuses seem fine and the fan moves freely. I don't know how to test the relays although I'm guessing it's unlikely they both failed at the same time. Is it time for a new fan unit?

[shogun]

The first and easiest check is for a seized motor, poke a tool through the grill and check if the fan blades turn. It ought to spin freely, if not it's junk. To check a motor that spins free connect ground to the brown wire and apply 12v to the blu/blk wire for the low speed. If it does not operate apply 12v to the solid blue wire, if it operates the motor is good and low speed resistor is open(bad).
If the runs only when powered directly by the jumpered connector amd hot coolant is circulating through the radiator, the radiator switch is faulty.

I had a problem some years ago that the fan was not running, did the above test first, also checked 2 fuses, still did not run. Then I used contact spray and sprayed the contacts of the 2 relays and the relay sockets, also the connector pins of the wire loom directly at the fan, that worked and the fanw was working again. So it was only bad contact at the relays.

Here Timm shows the connector at the aux fan, he also had a problem https://www.bimmerforums.com/forum/s...an-Not-Working

[SharkGill]

New fan resolved the issue thanks. Wasn't that difficult to do either.

[shogun]

today we fixed the aux fan on an E32 735, was not running in low stage, cause was oxidation of the pins of the low stage relay and the connector pins directly at the plug on the aux fan, used contact cleaner and enhancer and that solved the problem.
Before we made some other testing and found out, if stage 1 = low speed of the condenser fan is broken/not working, be not surprised that the 30A fuse melts when it starts immediately on stage 2 = high speed. There we measured in operation 27A and at the start briefly just under 50A!