Coolant fan doesn't use first stage

[Nero]

Getting mental of it, with the hot weather.

It doesn't use the first stage of the coolant fan, but directly goes to the second stage.

When the fan starts, a nice 300 rpm drop and a big jerk through the car when driving slowly...

When I park the car, and when the aftercooling starts, it's the first stage...

Which relais should I check? And what else could cause this?

[vertigone]

got the same, will follow this post

[Phil Payne]

It doesn't use the first stage of the coolant fan, but directly goes to the second stage.

Have to check the S2 wiring diagram, but the ur-quattro does this deliberately. Stage 1 is reserved for coolant pump or air-conditioning running.

[Fat Audi 80]

Have to check the S2 wiring diagram, but the ur-quattro does this deliberately. Stage 1 is reserved for coolant pump or air-conditioning running.

In which case I think the guys are referring to only speed 3 working. Speed 2 is effectively the one that cuts in and out at just over 90 deg's.

You KNOW when speed 3 kicks in as the car nearly stalls!

[Bram]

Nero is always blasting in his S2 so I can see why Stage 3 always kicks in

[Nero]

I drive it fanatic, that's true.

But the fan really kicks in hard. Not nice.

Would love to solve this.

[Nero]

In which case I think the guys are referring to only speed 3 working. Speed 2 is effectively the one that cuts in and out at just over 90 deg's.

You KNOW when speed 3 kicks in as the car nearly stalls!

It should be a relais or switch thing than I guess?

How does the thermoswitch for the fan works? Is it possible to measure correct function?

Relais should be changed I guess to be sure they work.

[LVrainman]

check if all the relays are in place in the relay box under the bonnet.. I solved my problem easily by putting in a missing relay..

[saltinot]

3 items to check here.....

thermo switch (on the radiator)
Series resistor (the large flat blue thing attached to the same bracket as the horns)
relays

I would start by checking all the relays. Then try jumping the connections at the thermo switch to determine if it is functioning correctly. If all that checks out you've either got a faulty resistor or a break in your wiring.

[Nero]

Thanks guys! Have some things to check now!

[jevrem]

I have the same problem. Where is the relay located for fan speeds. And what is the number on the relay?

[rs200]

99% it is NOT relay

100% bad thermo switch on radiator... but go in Audi shop and buy original ...

[kwlw]

It doesn't use the first stage of the coolant fan, but directly goes to the second stage.

Relays are rarely the cause of the problem. Thermo switch and resistor block are way more comon. I have replaced thermo switch on my a220v (alloy plate with three power resistors) to make fan first stage working. Good thing that resistor plate is same on audi 100/200 turbo no matter what engine it has. From what I seen in ETKA - same plate goes in S2/RS2.

Sau

[Audi-Porsche Avant RS2]

Hello, on my S2 Coupe ABY I have see that first speed is for afterrun and A/C when the temperature on the climatronic isn't set to LO, if I set it to LO the fan goes from first speed to second speed, I think that I have never see third speed or is possible that I have see it when I have bypassed thermoswitch for check if all of the two speed controlled by the thermoswitch work or not. So is all normally?
What can I do for check if really all the three speeds works correct?
Thanks!
Alessio