Heater on tick over

[green A8]

Now this is very strange, The heater motor on my 8 keeps going at a very slow speed even after the car has had the engine shut down, the key removed and the doors have been locked. Whilst this is very nice in the current heatwave, should it be doing this I've never noticed it before today. I can't say if it cuts out after a given period as I disconnected the battery to prevent it being drained. (I was in a very busy town centre and the last thing I wanted was a no restart due to a flat battery)

Before anyone asks, no I dont have a solar sunroof fitted to the car, just a normal steel one.

I will await answers with interest.

[Adrian E]

Is it definitely the fan motor turning rather than something else climate related like one of the motors trying to return to a default position, but masked by other noises when the engine is running?

Might be worth checking with vag-com/vcds etc to see if the flap motors are all behaving normally. Unless there's a voltage leak providing power to the motor still I'm not sure how it would be getting driven?

[HPsauce]

Could it be the "rest" function being triggered somehow, e.g. a faulty switch or controller? Try prodding that to turn it on and off for a start.

[PsYcHe]

Definitely the heater blower and not the engine fan?

[green A8]

Thanks for the replies gents and the helpful suggestions. I can confirm that it is indeed the heater fan that is playing up and not the engine fan or any other fan or motor.

This fault only seems to happen when the car has been parked in full sun and the interior has become very hot. I left the car in the garage overnight, started and ran the engine up to temp then stopped it no problem. no fan noise or slight breeze through the airvents. I checked under the bonnet and all was normal. I then took the car for a thirty mile non stop drive and returned it to the garage, again no problem on engine shutdown, all was normal. At this point the Wife suggested going down to our local garden centre as she wanted to buy a few items. I drove the car, again no problems we arrived at the garden centre and had to park the car in full sun. The heater fan still behaved itself. Wifey bought a load of stuff and took her time as per, so being a lazy bugger, rather than lugg it all the way to the car I brought the car to the loading area of the garden centre a trip of no more than 200-300yards. That's when it happened! the heater fan stayed on at the lowest speed setting. even though I'd switched the ignition off, and removed the key.

There's no display on the AC controls as the ignition is switched off and the key was out of the ignition. Pressing every switch on the air con unit yeilded no results, except 'rest' which performed as advertised, but turned the fan on to a much faster setting. On driving the car back home with the air con cooling the interior and parking up in the garage, the fault had gone away again.Everything was back to normal. Very strange.

So, any ideas gents? I'm thinking perhaps an overheated relay or sensor somewhere, as this fault only seems to happen when the cars interior is very hot.

I coupled up Vag-Com VCDS no faults were found.

I look forward to hearing what you make of this Gents, and await your further comments with interest.

Paul.

[Adrian E]

I can't see anything obvious to pull from the relay panel - maybe pull the fuse associated with the fan and see if removing power resets the fan motor?

It does suggest some kind of power leakage from the fuse board, or a logic problem with the controller in the climate panel.