steeler80

Sorry for the flood of "what about this" posts but, while I've always had old cars, this my first foray into Porsche ownership. I have done some searching on this issue but haven't found my exact problem.

I have an 85 Porsche 944. After I drove it home from purchasing it, when I parked it, the fans stayed on. I didn't think anything of it. When I came out around 20 minutes later, they were still on. The previous owner had said the fans hadn't been working so he replaced the relay and they had started working (including shutting off). I jiggled the relay and the fans shut off. Now though, they won't come on unless I turn on the air conditioning. Is it the fan relay, thermo fan switch, or something else I've not thought of?

herdy44

It sounds very much like a thermo switch or relay problem.
the fact that it comes on with air con switched means that the low speed fan part of relay is working.( I think it still goes through relay for air con activation)
also it means low speed fan resistor is working.

To check and eliminate the relay . Clarks garage has a great write up about bypassing the relay at the thermo switch connector to check both low and high speed fan operations.

If you jump them, first low ,then high , and the fans speed work as they should - relay is good.

Thermo switch activates low speed fan at around 92°C for and 102°C for high speed fan


Last month I was chasing a cooling problem,
thermo switch , relay and waterpump were replaced and radiator removed and flushed.
it was a right pain

orig944

Early 85 (square dash) or late 85 (oval dash)?

steeler80

Square (924 type dash).

orig944

Good, I also have an early '85 and can help you.

First, look at the A/C section of the '84 944 schematic on Pelican. https://www.pelicanparts.com/944/ele...4_AC_1.jpgnand
https://www.pelicanparts.com/944/ele...44_84_AC_2.jpg

(Your car is identical to an 84, l and I recommend you use 84 when you are ordering parts as some places will send you parts for the late '85 if you say '85.)

Your radiator thermo-switch is on/off, as opposed to newer 944s which have two outputs (low and high.) Since both (hopefully) both fans run when you have the A/C on means that most things are working. If so, both relays are fine. If the engine is hot and the A/C is off, both fans should run if the ignition is on, and one fan should run at low speed if the ignition is off until the radiator cools off.

The fans are pretty loud on early cars, it might sound like both are running when only one is (our cars have three blade fans, later cars have six blade fans that run slower.) 20 minutes is a long time for the radiator to cool, so the thermal switch is suspect.

walfreyydo

Have you read through this and done the testing procedures for the switch and fan relay? It could be the relay but it could also be the thermo switch. Need to test both. Thankfully, clarks has a very clear and concise way to test, which I would recommend you follow:
http://www.clarks-garage.com/shop-manual/cool-01.htm

steeler80

Sorry for not replying back sooner. It was the thermoswitch. I replaced it and now the fans are working properly. The left side fan comes during normal driving. When I shut the car off, it runs for a few minutes (no longer than two or three) and then shuts off. I don't think the second fan has ever come on for normal driving but does work if I turn on the ac.