Another Air Con Question.

[benjie]

I've trawled the forums looking for someone who has my symptoms and I can't find one that fits.

The problem is with the central vents. When I adjust the temperature so that the car is providing temperate/cold air, they work fine. When I increase the temperature so that it's providing heat, all air from the vents stops... until the ambient temperature is reached and the air con goes back to proving temperate air, in which case it starts again.

It doesn't matter whether the engine is cold/warm or how long the air con has been on, it will do it whenever the temp is increased.

I'm guessing it's a flap, but I didn't realise that there were 2 flaps - one for hot, one for cold?

Can anyone shed any light on this for me please?

 

[quattro tony]

Might be worth doing a scan of the heater system, do you have vcds?

 

[benjie]

Yes, sorry, I shoud've said. No codes are present in Auto HVAC. I did have the Air Con recirc flap fault code a few months ago, but I went into basic settings and got the motors to realign and that code went away.

 

[quattrojames]

I have an intermittent flap motor for the windscreen demister, but it always shows up in a scan, so not sure it would be that, although it does sound like it. Have you looked for a pipe thats come off or anything like that?

 

[benjie]

No I haven't looked yet James, I'll be doing it next weekend. I've had the dash off before though (don't ask) and there's not really any places where a pipe could come out. The car has like a big hard plastic box with 3 holes in the top for the air to come out and on the dash there are corresponding holes that slot into each other. They're plastic welded (or similar) so no real opportunity to pop off*

* This time next week I bet I'll be commenting on a popped off pipe!

 

[quattrojames]

I'd be surprised if it was that in fairness.

Take the glovebox out, get down in the footwells and move the hvac controls and see what motor controls what flap etc.

 

[benjie]

Will do. I have a friend with a B7, so I think I'll get him to do the same and we'll see if the same things happen!

 

[AU01 A4]

could it be an air lock in the heater matrix?

 

[benjie]

I have no idea. Would that cause localised loss of hot air? Do you know how would I check for that?

 

[benjie]

I've managed to get a motor for my car, the one that showed up on a scan last week... the central flap motor. Once it's fitted, does anybody know if I have to do any special procedures to calibrate it to the car? Or is it just a case of doing a flap alignment in Basic Settings? Does anyone know?