When the cooling fan relay fails, is it with the fans always running or always off? We just replaced the temp switch for the fans on Jeff's NA, and it still runs the fans when the battery is connected... My initial thought was that it was the relay... Sooo... to avoid that, does anyone have a spare, OR does it sound like something else?

Thanks!
-Geoff

 

Relays can fail open or closed. It can basically weld the contacts together because of arcing if enough current is passing thru it. And then whatever it controls depending on other switches or relays can stay on all of the time. Also wires can melt together and cause the same symptoms.

Did you test the thermal switch before installing it?

Did you unplug the thermal switch to see if the fans keep running?

 

No we have not. We'll go ahead and give that a shot real quick...

Jeff is running a 6 blade fan, so if it's running a stronger current, that could be the cause of the relay failing...

 

quick question...where's the thermal switch?

 

quick note, I just checked Paragon and Pelican, and both are selling a later fan relay...this problem is occuring on an early 1985 car.

 

Jake, are you thinking for the cooling fans? If so, that's mounted on the radiator under the top hose on the driver's side, directly to the left of the cooling fans when looking at them. more than halfway up.

 

ohhh ok. that's what i thought it was. thanks geoff. that is what signals the cooling fans to run am i correct?

 

He's busy playing GT4 on my PS2 so I'll answer here - yes the sensor sends the signal to the cooling fan relay and from there to the fans (the presence of the relay is to allow smaller, lower-current wires to run to and from the sensor, thereby controlling the higher current (through suitably larger-sized wires) to the fans themselves. The relay is kind of expensive so I'm hoping that's not what has failed, but it probably is. Tests are forthcoming.

 

When I had an "always on" fan condition on my 924s, it was because the sensor (that screws into the radiator) failed.

 

If the early fan relay is the same as the later one, you can check out this thread that I made a while ago. It tells you how you can test your relay. All you need is a few wires and a multimeter. That thing is too expensive to just "go and buy a new one."

 

I've replaced 2 this year. The first came with the car. It wouldn't close so the fans would never run. The replacement would get stuck closed and run the fans continuously so I had to pull the battery when the car was parked. Eventually, it would reset itself until the car warmed up enough to close it again. So far, switch #3 is working fine.
If you follow the diagnostic procedure above and check out the relay, you can't go wrong.

 

Here is what I am experiencing, any help appreciated.

My '89 944 S2 is doing the following: start-up from cold (85 degrees in S.W. FL) and no fan running. Once I switch the A/C on the high speed fan comes on runs for approx. 10 seconds, then shuts off for approx. 5 seconds, then repeats the cycle until I turn the car off. There is quite an electrical draw when the fan comes on; which registers with a drop on the volt meter from just under 14 to just above 12.

It seems that if I start the car and do not turn the A/C on the high speed fan does not come on immediately, but with the heat and humidity here; the A/C is always on once out of the garage.

Any thoughts?

 

It certainly sounds like something is amiss here. I'm not an expert on the S2, but I believe with the a/c compressor engaged, the fan should be on continuously - not cycling as you describe.

The part about no fan running with the engine cold is normal - assume "normal" operation without using the a/c at all - the system SHOULD leave the fans off until the coolant heats up enough to trigger the sensor (one on the radiator), at which point the fans kick on - even if there's no a/c running.

I would try replacing the relay. . . You may also have a ground issue or something - probably someone else with more knowledge will chime in here. . .

 

The electric radiator fans are supposed to run when the A/C is on. On my 84 I am pretty sure that they don’t cycle but they stay on all of the time. I wouldn’t know because I am not driving around with my head under the hood and my fans are too quiet to hear over the engine and the A/C.

How do you know the voltage drop isn’t the A/C compressor cycling on and off. Are your radiator fans that noisy? I have read about people talking about changing to the 6 blade fans to quite them down. I don’t know when they made the change if it was the earlier models to the later models or the other way around. All I know is when I bought mine it already had the 6 bladed fans.

 

Wow... can't beleive this was resurrected... Damn... a relic from my Long Beach trip.