repairman

I originally had heater control problems with my 1992 C4 and applied Tore Bergville's tests and found (amongst other problems) that the oil cooler fan was not functioning. I had the CCU and two servos overhauled by PARTisan.

When I tackled the oil fan I found that the fan connector was not plugged into the fan. Now what is unusual is that I have owned the car for fifteen years and no work has been done on the fan. By feeling with my hand I also found that the ballast had disintegrated.

After reconnecting the fan plug I jumped the connection at the relay again to test that the fan was operating at high speed.

I went the path of Garth S and made up a replacement module out of two 50W wirewound resistors.

This time by jumping the connection at the relay the low speed fan setting worked.

But, when I turned the ignition on the oil cooler fan was cycling at the high speed setting. Swapping the relays made no difference.

A Tore Bergville article suggests that this indicates a faulty resistors! Does this mean that I should use a genuine resistor or is there another problem?

greg1990964

I would guess resistor. I am replacing mine in both fans as soon as I am done with suspension upgrade and valve adjustment on the coupe. Hope that it solves my issue.

TideRace

I picked up a '90 964 C2 recently and the oil cooler fan was cycling on/off at high speed only. Faulty resistor was the culprit.

Rocket Rob

When my coupe's AC cooling fan began cycling, I discovered that the fan's ceramic resister had disintegrated. I replaced it and the fan began to operator normally. Its my understanding that the oil cooler fan has a similar ceramic resister. I would replace that if yours is crumbling.