Thermo/Cooling fans going when car off

[RSV001]

Hey guys

So im having the 'old thermo fans coming on when the car is off'.
Firstly my car is: 2009 S3 3 Door
Backstory is: It started happening out of the blue about 6 weeks ago....
I came here, searched around, others seemed to have similar problems, except in mine, both fans were coming on full speed, which, the solution seemed to be, the fans were on their way out.
Easy, go down to my parts place, pickup a secondhand fan assembly from a car with faily low k's.
Wrong, i installed and the problem continued.
So it ****** me off for a few days because the day it started happening was the day i was to flash my first tune...
Few days went by and i wanted to get to the bottom of the problem but i had the far fetched idea that MAYBE the tune somehow magically would stop this from happening.
It did and i was of course more than happy..

So that was 5 weeks ago and id completely forgotton about the damn fans when it started happening today again.
No sweat, ill fix it up, ill reflash the tune itll go away for sure.
Nope, it did not.

btw when the car is running, the fans work as they should, they come on and turn off as they should - they work normally.
which is why - i assume - that VCDS has reported nothing - before, after or now, and i run it quite regularly. And i suppose why would it? When the car is on, which VCDS must be to be run, things are peachy..

So whats my next move here? Coolant sensor? I dont wanna do it unless i have to, i cant even find it in where its supposed to be, it looks like an ******* job, but if it must be done then it must.

Cheers for any input and in the meantime ill reinstall the switch i made up to kill the fans when im not in the car.

 

[aqibi2000]

Car off AND locked, fans continue to run indefinitely afterwards or for 1 minute ?

 

[RSV001]

It does it both with car locked and unlocked and sometimes both fans but sometimes just the small one. Its really random. It def goes longer than 1 minute.

 

[SootySport]

It won’t be anything to do with the fans, must be a sensor or timer that is faulty. The wiring could also be trapped and shorting to the chassis. Have you timed how long the fan runs after you lock the car? Does it make any difference if air con is on or off?

 

[prt57]

I have a prefacelift S3. As part of updating the gear cable connections, I unplugged the connection from the temperature sensor above the gearbox to give me a bit more room.
On plugging back in the sensor the fans started on full blast. Only way to stop was to take the negative lead off the battery.
A quick change of sensor sorted the fans out with an Audi OE part.
There must have been a dodgy joint etc in the sensor and pulling off the connection to give me more room must have dislodged something internally.

 

[RSV001]

Does it make any difference if air con is on or off?

Nah same on or off.
Update, i replaced the sensor above gearbox, the easy one to do, it didnt change a thing. $130AUD wasted...
Is the one on the other side different? I suppose ill have to just do it now

 

[RSV001]

The wiring could also be trapped and shorting to the chassis. Have you timed how long the fan runs after you lock the car?

Sometimes as soon as key is out, they come on, sometimes 1 sometimes both fans....and sometimes, like after i did the plug yesterday, and thought itd fixed it - they didnt come on till 20min or 30min after key was removed.
Could it really be wiring issue, since when car is running they function perfectly?

 

[aqibi2000]

Sometimes as soon as key is out, they come on, sometimes 1 sometimes both fans....and sometimes, like after i did the plug yesterday, and thought itd fixed it - they didnt come on till 20min or 30min after key was removed.
Could it really be wiring issue, since when car is running they function perfectly?

Please don’t throw money at it with sensors, also I would have bought a second hand sensor for something so insignificant.

Did they come on at MAX speed? Because this happens when the PCM is offline and no long modulating/controlling. I see this often when flashing the pcm. Basically when the pwm line is pulled to high/low depending on the implementation the fan comes on...

Please confirm the above fan Rpm question, as it could help understand if you have a harness issue specifically for the control wire of the fans

 

[SootySport]

So if the Fans start up after 20mins then it’s not a run of the mill problem. Specialist diagnostics required here, something that we can’t answer I’m afraid.

 

[Daveyonthemove]

The only time I have had any issue with the fan coming on at full power with no reason was when I loaded a Bluefin remap to the car and the file had not downloaded correctly, effectively 'bricking' the car.
This doesn't sound like the same issue, but it is worth asking if your car was remapped prior to this issue starting?

 

[William McGougan]

Sorry to jump on the thread, I have a similar issue, both my fans come on as soon as I start the car even from cold and stay on until I switch off the car? Ignition on and they don't come on, only when engine running so any ideas what it could be? As I don't have any fault codes on VCDS and temp gauge reading fine on dash

 

[aqibi2000]

Sorry to jump on the thread, I have a similar issue, both my fans come on as soon as I start the car even from cold and stay on until I switch off the car? Ignition on and they don't come on, only when engine running so any ideas what it could be? As I don't have any fault codes on VCDS and temp gauge reading fine on dash

Crappy DPF deletes can make the car think it is constantly regenerating (since they delete the sensors you cannot locate the dtc for a bad sensor) then fans can come on. Diesel

 

[William McGougan]

Crappy DPF deletes can make the car think it is constantly regenerating (since they delete the sensors you cannot locate the dtc for a bad sensor) then fans can come on. Diesel

My car is a petrol S3 mate, same as the original thread posters car, I just wondered if anyone had a solution as my problem is very similar

 

[RSV001]

Please don’t throw money at it with sensors, also I would have bought a second hand sensor for something so insignificant.

Did they come on at MAX speed? Because this happens when the PCM is offline and no long modulating/controlling. I see this often when flashing the pcm. Basically when the pwm line is pulled to high/low depending on the implementation the fan comes on...

Please confirm the above fan Rpm question, as it could help understand if you have a harness issue specifically for the control wire of the fans

Sorry bout the delay in replying my license was stolen from me by the courts for a breif period.
Yes confirming max speed
Also confirming BOTH plugs have since been replaced with new ones and the problem continues to occur

 

[RSV001]

The only time I have had any issue with the fan coming on at full power with no reason was when I loaded a Bluefin remap to the car and the file had not downloaded correctly, effectively 'bricking' the car.
This doesn't sound like the same issue, but it is worth asking if your car was remapped prior to this issue starting?

Wasnt/hadnt been mapped when it started happening.
Flashed map out of impatience and curiosity and like magic, back to normal...
2 months later out of nowhere it returned

 

[RSV001]

Sorry to jump on the thread, I have a similar issue, both my fans come on as soon as I start the car even from cold and stay on until I switch off the car? Ignition on and they don't come on, only when engine running so any ideas what it could be? As I don't have any fault codes on VCDS and temp gauge reading fine on dash

If my fans are going off full speed all locked up and no key in, as soon as insert the keys and first click theyll stop and during driving continue to operate as normal until igition off/keys out so possibly differnt problem?? maybe?? almost the opposite of mine but equally strange