Does anyone know what circuit triggers the auxillery
fan at 110C. It does not go on. Jumping the fan with
12 volts makes it spin, so it is working, however it will
not come on when temp guage reaches 110C at idle.:(
Fuses are good in box.
Any ideas???

Gary

1. Double check the fuses. There might be a hairline crack or bad contact.
2. Unplug the two pin coolant sensor. It's either on the head or water pump. If the fan turns on you probably have a bad sensor.

Vinamg

Vinamg,
Checked what you suggested, fan spins. Found bad cube relay.
It was clicking but not engaging. Replaced it and everything works fine.:) :)

Thanks,
Gary

I'm glad it worked out and everything is back to normal.

Vinamg

Glad it's now fixed, but just so you'll know;

The aux fans are usually turned on by excessive high side refrigerant pressure, not cooling system temperature. In some models either high side pressure OR high coolant temp will turn on the fan.

Good luck,

Larry,

You are correct, but the refrigerant sensor triggers only half speed via resistor. Once the temperature gets really high it is triggered via coolant sensor directly to aux fan for max speed.

Vinamg

Vinamg...

on my 92 400e, the fans never come on, even with the sensor unplugged!?!?!??? ;-( any suggestions other than the fuse box????

thanks...peter

You have to check the relays.

Vinamg

So,

Are you saying that the fans "SHOULD" turn on when they are unplugged from the CT Sensor? I mean, that's what's happening to me, but I thought that was opposite of what was supposed to happen.

Also, the blue part of my CT Sensor turns withing the brass piece. Is this normal? I think I'll go ahead and replace it. Does anyone have ANY idea where I can get a new one? No one seems to know... especially my dealer.

Willy

That's correct. The fans turn on when the sensor is in open loop or when unplugged. The blue part of the sensor should not turn. You should definitely replace it. I am very surprised that your dealer doesn't carry it or at least order it for you. Try to order from Fastlane.

Vinamg

Thanks for the tip. I'll go ahead and replace the CT Sensor as soon as I find one.

At least I know that the fans work. Since my car does not reach the 107+ temperature range too often, I was not sure if that sensor was working. But since I did the "resistor" trick, they do come on. Again, I'll still replace the CT Sensor as it is turning within the base.

So now I need to find out why fans don't come on when the air conditioner is on and running for a while. I just had the Expansion Valve and Receiver/dryer replaced and then a vac and fill. Finally, cool air!

There seems to be 2 sensors on the Receiver/dryer. I'm wondering which one of the 2 controls the aux fans and how to test to make sure that the wiring and sensor is ok. Any idea?

Thanks

Willy

ok,

Answering my own questions, when the wires on the high pressure switch are jumped, the fans turn on at half speed (assuming all else is well). Mine did not go on, so I went on over to the Aux Fan relay and found that the top wire was rusted and crumpled in my hand. Once cleaned and connected, the aux fans turned on.

After a small bit, the resistor began to smoke... probably caused by all of the rust/corosion. I'll go ahead and replace it as soon as I can remove the bottom screw. The only way to get to it is to first remove the coil cover. Any ideas on how this thing comes off?

Willy