Dennis Burford

Hi again,

My aux cooling fan is running as soon as I turn the key to "on". Can't seem to find anything in the archives that matches this symptom. It shuts off as soon as I turn the key off, no run on. I've disconnected it for now. Where should I begin to look?

Thanks,
Dennis

ZEUS+

First thing to check : Pull relay XVIII and see if fan stops. Swap in horn relay XII . If fans dont run with horn relay, fan relay is stuck closed. Did it do this before you by-passed the freeze switch ?

joejoe

In other post you have bypassed freeze switch, thus calling for a/c at all times. Aux fan will run by cooling temp if high, a/c running /pressure. Aux should run with a/c.

Dennis Burford

Yes, it did this before I bypassed the freeze switch. I'll try the relay swap, thanks for the tip Zeus.

Dennis Burford

Tried swapping fan relay out with horn relay and still have the symptom, aux fan comes on when key is turned on. Could there be a bad engine or radiator temp sensor that is causing this?

Thanks,

CAShark

..

WallyP

There are three (or four on the auto transmission cars) temp sensors that trigger the aux fan.
- Radiator temp sensor, located in the lower corner of the forward face on the driver's (USA) side of the radiator. Operates only with the ignition on.
- Torque converter temp switch. Operates only with the ignition on.
- Refrigerant temp switch, located on the receiver/dryer. Operates only with the ignition on.
- Intake air temp switch. Operates with the ignition on or off.

Your problem is almost certainly one of the first three sensors. The easiest test is to simply unplug each of the sensors until the fan stops. With the engine cold, engine not running, turn the ignition switch on, and unplug the sensors one at a time. When the fan stops, you have found your problem.

Dennis Burford

Thanks Wally,

My fan is not running after the ig switch is off so I'll look at the rad temp switch first and then coolant temp switch. I'll post back with results.

Dennis Burford

OK, I disconnected the rad switch - no change.
Disconnected what I think are the intake and coolant switches - nothing. Altough I could be pulling the wires to the wrong sensors. I thought I'd saved a diagram schematic to what each sensor was in the engine bay but I can't find it - can somebody point me to that helpful piece literature?

Thanks,

Mako 928

Any update to this?

Dennis Burford

Hi Greg,

Yes, it was the AC temp switch, the switch on the stem in the front of the radiator. It is changeable without loss of coolant, which I did, and stopped the fan from running. Unfortunately the aux fan on 86 and older cars don't run automatically when the AC is switched on, only when AC or coolant gets too hot, so I am considering the AC relay mod to cause the aux fan to come on, and give that little bit of extra cooling to the system.

Mako 928

Hey dennis,

Thanks for updating this as I am currently trying to get my auxiliary fan to come on. I should have talked to you about this at SITP.


What is the AC relay mod?

BIMMERMIKE

" Unfortunately the aux fan on 86 and older cars don't run automatically when the AC is switched on, only when AC or coolant gets too hot, so I am considering the AC relay mod to cause the aux fan to come on, and give that little bit of extra cooling to the system. "

Can you post the wiring diagram of how you plan to achieve this?
I want my auxilarY fan to turn on when AC switch is ON.