944 overheats when a/c is off
 

My 944 overheated today on the way to class. I had my a/c off and both cooling fans were not running even at the temperature gauge 3/4+ level. I drove home after class (and after the car cooled down) with the a/c on and the car ran at normal running temperature.

The cooling fans run when the a/c is on, but when the a/c is off the fans will not turn on and the car will overheat. What is wrong with my car?

Could this be a theroswitch problem?

http://forums.pelicanparts.com/showthread.php?s=&threadid=73662&highlight=a%2Fc+c ooling+fans

http://forums.pelicanparts.com/showthread.php?s=&threadid=51958&highlight=a%2Fc+c ooling+fans

thamlin's on the right track.
It's either the thermoswitch (upper drivers side of radiator under upper hose)
or the fan relay.

924S Bob

Dont forget to check the fuse/fuse holder. My 944 had built up some corrosion on the fuse ends in the holder which caused my fresh air blower not to work.

Do the easy thing first. Check/replace the #3 fuse on the upper (smaller) fuse bank.

If this does not work then your thermo switch has probably failed open (off).
To check this, remove the wires from the thermo switch and jump them with the ignition on. BE VERY CAREFUL! If this is the problem your fan will come on and chew up anything it is in contact with e.g. your fingers (or is it i.e.???).

If all this does not work then you have a wiring problem (break out the multimeter) or a bad fan motor. But, I'll put my money on the fuse or the switch.

Thanks everyone for the input, time for me to start troubleshooting.

similar problem
 

I'm having the same problem with my '90 cab. It overheats *sometimes* when the A/C switch is off. I've already replaced the thermoswitch and the fuses all test out OK.

Would a relay problem or bad wiring affect the fans regardless of the state of the A/C switch, or is that all bypassed? My guess is they would cause a problem regardless of the position of the A/C switch.

As always, thanks.

I finally fixed an intermittent high temp problem, it finally went into the red zone I had to turn on the A/C to bring temp down. I replaced the Cooling Fan Relay and now, the fan operates for a period of time after the ignition is off when engine is hot and the fans come on a bit past the first hash mark during normal driving.($122.00 relay/ incl. tax).

Obviously it's not a fuse if your fans operate with the AC turned on, don't know who suggested that. Just pull the plug from your fan switch and short the leads...shorting leads two and three should give you both fans at low power and shorting leads one and three should give you both fans at high power with the ignition key turned to the first position. Testing the relay is a bit more difficult but the switch is a place you can start. If you're still not getting fans then it's the relay, I don't think it's your resistors though.

Just realized you have an early car but the same basic idea applies. I think you have a two prong temp switch but short those leads from the switch and see if you get the fan[s] to operate.