Hi - I'm new to posting in this forum, though I've beeen lurking and picking up valuable info for over a year now. Vehicle is an ex-track-car '89 944 NA, which has a host of electrical gremlins which I'm trying to pick off one by one. My latest project is to clean up all the chassis and engine ground points, and in the process of doing so, I discovered the following (to me) mystery.

Upon picking up the plastic cover over the wiper motor and heater ductwork, etc., I noticed a clump of badly burnt wiring on the upper passenger side of the firewall, connected to two items which I can only describe as squared-off ceramic doughnuts (they look sorta like stubby canned pineapple slices). I have no idea what this assembly is, nor what problems the burnt wiring may be causing me. Can anyone point me in the right direction?

 

Those sound like your cooling fan resistors. Do they look like this?

 

yep dat be dem

 

Yes, that's them. My cooling fans seem to be working OK, but I don't see how, since that wiring is completely fried. Guess I'd better rewire and perhaps replace the resistors - wonder what could have caused the burnup?

Thanks for the info.

 

OK, second question. If I'm reading the wiring diagram correctly, these resistors are simply placed in series with the two fan motors when slow fan speed is required. They would seem to be connected into the circuit via2 pairs of terminals on the fan relay. Therefore, it would seem that even if the resistors were completely shorted, all that would happen is that you'd get fast speed when slow was called for. All 4 wires are completely fried. I can think of only two explanations - the relay is somehow routing +12V directly to ground through the resistors (but if so, why isn't the relay fried also), or the resistors themselves got so hot that they burnt op the wiring (but it's burnt all the way down into the harness). Any ideas?

 

Every car that I have taken apart has the wires burned to a crisp but the resistors themselves are fine. I don't have an explanation as to why. I just slip some heavy duty heat shrink tubing over them and keep on trucking.