V8_Macguyver

ok, for the past six months my car has been overheating at the worst times, it's a 1991 AudiV8 Standard transmission. i've replaced all of the relays, flushed the radiator, and pretty much did everything i could think of, recently i discovered that the electric radiator fan doesn't kick on unless i make it kick on by turning on the a/c, even then it's very weak and makes a 'rattling' noise. my question is, what are my options to fix this, and what part might i have to look for, the entire assembly or just a clutch of some sort. thanks for the help in advance, i'm gonna go look at my huge shop manuals right now and see if i can't find a description with pics of what i might need.

ryan

itsav8

You'r radiator is clogged!!! Period end of disscussion. Your fan is working as it should.

$300 from Mr Semple at forc5 will take care of this problem.

Kneale Brownson

The motors in the electric fan can have their bearings replaced. If you remove the fan (two bolts with 10mm heads and disconnect the power supply), you can take it to a Bosch repair center or replace the bearings yourself if you have that capability.

As Ron notes, if the car overheats, you most likely need a new radiator. The V8 radiator is famous for clogging internally.

V8_Macguyver

i've had the radiator flushed and had a mechanic look at it, it really doesn't appear to be the radiator, i took off the expansion tank and let the water pour out, it was really pumping through, the fan is rather noisy and isn't spinning that fast, so i'd imagine it would be the fan, what needs to be replaced on the electric fan

V8_Macguyver

also, if the radiator in fact was clogged, wouldn't the thermoswitch try to kick the radiator fan on anyways? it won't come on until it gets almost to a hundred degrees celcius, even then it only runs for a bit, the only way to get it on and keep it on is to put the a/c on, even then it's very noisy and doesn't sound like the jet engine that it used to

audiqv8

"if the radiator in fact was clogged, wouldn't the thermoswitch try to kick the radiator fan on anyways?"

No No No

The thermoswitch which controls the fan is located at the bottom of the radiator (passenger side) and by the time the coolant does gets to the thermoswitch,it has already cooled down and the thermoswitch doesn't see an overheat condition. Carefully check the top and bottom hoses to the radiator. They both should be very very hot. My guess is that the lower hose is warm or even cool.

Remove the wiring connector to the thermoswitch on the radiator and use a 100 ohm resistor to short the connector, this will cause a overheat condition and the fan should go to jet plane taking off.

Fair Cape-Cape Town

In fact just change it, for what it costs the peace of mind is worth it.

V8_Macguyver

Thanks for the info, but i'm already ahead of you, i replaced it for around thirty bucks, you're right, the peace of mind is worth it, unfortunately it wasn't the culprit

Fair Cape-Cape Town

There should be two relays. One will activate when the thermoswitch closes on its low temperature setting sending power to the fan via a resistor plate to give low speed fan.
The other relay is activated by the thermoswitch high temperature setting and the second relay will send power to the fan directly giving high speed.
If you trace the circuits you should find the fault.
Common failure is the resistor plate.