Dr. Dynamics

Does any one know the working logic for the cooling fan relay and what are the two big resistors on the pass side exactly for (I think lowering the fan speed)?

I found the four wires for the resistors with all the inside wiring exposed. When I was going to fix it, they practically became sand on my hands.

I was cheking the manuals out in order to see if something can be done, but I still have my doubts on the relay logic.

Thanks

Bri Bro

The cooling fan relay places a short across the resistor to turn the radiator fan on high speed. There are two resistor because there are two fans. Without the short, the fans runs on low speed.

944TTwin

where exactly are the two resistors, i tried finding them on my car, i read some where that they are behind the glove box. i took out the glove box and couldn't find it, can someone tell me where they are in respect to the yellow box behind the glove box.
TIA

hosrom_951

944TTwin: On 86 cars (i believe), you need to remove the glove box, lay down on you're back and look high up at the firewall of the passenger side, i also believe there are three wires going to each restor, they look like white donughts.

Later cars have them behind the battery, in the engine compartment.

Bri Bro

If you slide yourself all the way back to the firewall on the passenger side, you can look up and see it. Here is a picture taken without removing the glove box.

gregeast

There's a very detailed write-up at www.clarks-garage.com on cooling fan operation and troubleshooting. IIRC it's under 'Cooling System'

Dr. Dynamics

Thanks beab...

Actually, I had cut off the resistor wires thinking it was the low speed due to lower current through that circuit. I really don't explain how it did not burn the car up since they had INCHES of exposed wiring. Now I found that my fans aren't working at all. I grounded the connector at the temp sensor and they worked. Guess I have to order a new sensor now...

Dr. Dynamics

gregeast, thanks for the link... GREAT INFO SOURCE!

For clarification purposes, sorry bean..., I think youre the other way around, check out clark's garage link to Cooling System/Fan Operation/ Late 944

The slow speed is through the resistor circuit...

Bri Bro

I think that is what I stated, the fan relay making a short across the resistor is high speed and without the short, ie the circuit is through the resistor, the fan runs on low speed.

951Porschiste

My car is an '86 and they're behind the battery.

944TTwin

thanks guys i have a 87, hopefully i find them behind the battery, b/c they are not behind/above the glove box and if someone has a pics of the resistors behind the battery that would be great

Dr. Dynamics

Has anyone had the same thing happen to those wires. They are 2.5 gauge wires. In relation to the rest of the car's wiring, those four wires are pretty crappy stuff...

hosrom_951

On my 86 the resistors are behind the glove box

I know they changed the location, but not sure which year(s) or models were changed.

Bri Bro

The picture above is from a 86. I will look at the 87 but I think it is in the same location. There is another resistor pack under the plastic shield next to the firewall. These resistors are for the interior fan motor.

944TTwin

I FOUND IT, thanks guys