Help: Radiator Fan Problems

[AudiRS]

I`ve got this problem with my Coupe 7a 20vQ. The watertemperatur was a bit off when I bought the car, so I changed the thermostat and bleeded the system. Now the driving temperatur is good, but when driving slowly in rushtraffic or when standing still for a while it`s getting to hot (about a 100 degrees).

I`ve found the problem, but not the solution.
The radiatorfan does`nt come on when the engine is on, even if the temperature is getting near a 100 degrees.
Is this a sensorproblem maybe? Is this the sensor wich is found on the lower rad on the radiator?

The second problem is that when I turn off the engine the fan goes on with full power. It also turns it self off and on as it pleases after being driven, more than normal. So mutch that the battery is being affected.
Is this the sensor behind the engine, on the top?

Can anyone tell me how this fan-system works and the fuction of the sensors?
Any tips and tricks?

[macspring]

my suggestion would be to buy a new fan switch which the unit at the bottom rear side of the main radiator with the three electrical connections.

The switch is relatively inexpensive and it can't do any harm having a new one, particularly if the exiting one is the original one.

Then see how the car behaves and posts any results or changes in this thread, then the next step might be more obvious.

HTH.

Kind regards.

[Paulgo]

That afterrun fan running after switching off is normal I believe on a cq20v - my 7a used to do it. Is a wierd thing tho! I would park up, walk away from the car and then fan would scare the cr*p out of me as it suddenly jumped on of its own accord!

Could well be the wiring to the fan switch at the bottom of the rad for the other problem - from its position it gets covered in a lot of crud. I had a similar problem and the terminals in the switch plug had corroded away, so no wonder it wouldnt work. Replaced with some flat, unshielded spade connectors into which I resoldered the wiring, and all was good. Just a thought before replacing the whole switch.

good luck

Paul

[simon20vq]

I second PAULGO, 7A fan come on with ignition off (theres a label near rad that says something like watch your hands! I would also check the wiring to switch as there could be a break in one of the wires. Maybe worth checking if there is a current there with a test light. You will need to do this from under neath the car. switch is near n/s wheel side of rad.

[AudiRS]

Thanks for tips!
I have checked the wiring down to the sensor, and its ok. But I will have an other go at it soon. I think I`m going to listen to Daving and buy this switch so we can eliminate this as a problem. It`s just to bad that new parts from Audi cost so god damn mutch in Norway

I know this after-run-fan is a feauture on the 7A 20v, but I think it goes on too long...and at weird times..
I`ve checked the pins and sure there where some corrosion there. Cleaned it to pure metal, but I`m going to change the connections with some new ones

A question: The switch on the radiatior is only to the fan when engine is on? And the sensor on the top rear of the engine (wich stand in open air) is for the after-run?
Yes or no?

[AudiRS]

Well, I`ve changed the switch without any luck, the fan still does`nt start when the engine is on.
I measured no electrisity from the switch`s contact so the fan does`nt get any signal from the switch.
Checked the fuse and it was OK, but wich one is the correct relay for the fan?
Anyone got the Wiring-Schematics for the fan?

[hermanio]

maybe this will help you, does the fan run when you put 12v on it ?

http://www.isham-research.co.uk/quattro/wiring/TypB4/08_luefter_zusatzinstrumente.jpg

[AudiRS]

The fan goes on at after-run, so the fan works yes!

[AudiRS]

Looks like I need som help here. I`ve found the afterun-relay, but not the relay for the fan? Is there any hidden fuses to look for?
Anyone got some info on this? I recon its the same for most S2`s!

Tested the fan with direct 12v, and it works at both speeds.

edit:
At the looks at it, the wiring-schematic Heramanio found says that its 12v by ignition on the Thermoswitch. So if there is`nt measured any electrisity by the switch, it meens the relay does`nt work either?
Where can I locate the 15A fuse (before the switch)?

[AudiRS]

Found the problem! It was a wire to the Thermoswitch which was thorn off..
Now the fan goes on again.
But I`m still not satisfied. The engine still get some what kind of hot before the fan goes on.
It goes on at aprox. 97,5 C degrees and keep it there.
On wich temperature shall this fan actually go on?

The problem is still only in rushtraffic/standing still with engine on. When getting some speed the temp goes down to more normal 90 degrees.

[AudiRS]

Anyone?
The fan goes still on a bit late

[AndyP]

Are you using a new MFTS? The new ones seem to make the temp gauge read high, on the ones I've used they make the fan come on at 2-3 line above 90° on the gauge, swap back to an OE MFTS and the fan comes on at 90°.

[AudiRS]

The multi-temp.sensor (if thats the right sensor you are revering too) is`nt changed. It`s an old one, but if its changed by an privus owner, i don`t know