A4 Demister problem

[scorpio]

I have a 2002 Audi A4 Avant 1.9 TDi and have a problem with the
de-mister part of the climate control.

About 10 weeks ago, it suddenly stopped working, but only on this
setting (all other vents and temp settings worked fine). The fan blew hard and air came out of the top side vents but not from the single vent which clears the screen.

Suddenly, about 5 weeks ago, it magically started working again (I
made no changes that i am aware of) but as of last week, decided to
stop once more.

I had a chat with my local Audi/VW specialist who suggested it may
be leaves blocking a vent (we have a couple of overhanging trees) or
a rain water issue or a hose that has come loose (the sudden working
of the vent suggest this is not the case).

Of course, it could be a sensor/electronic issue.

Obviously, I dont want to get into a 'dashboard out' situation if it
can be avoided. Are ther any tests I can carry out to diagnose the
problem or do you have any other suggestions?

Thanks for any help you can provide.

Rgds,
Scorp (1st post):1zhelp:

[Sky]

Scorp. Can I refer you to my thread currently running, sounds like we have the same snag. Will let you know if I have a recurrent failure and if the same trick of charging down the motorway and changing the output temperature works.

Sky ;)

[RickT]

More than likley it will be a flap sticking,.,,,, if not sticking.. a fault unit controling the flaps for the windscreen..

If you put it onto VAG-COM you can check all the flap status and check any faults..

RicKT.

[scorpio]

Thanks Sky and Rick. I am sure rick is correct as all the temperatures (hot through to full chill) and other air channels work fine. To get the car on VAG-COM, do i need to pop down to my local Audi/VW independent or is this a main dealer job?

Rgds,
Scorp

[gary2262]

If everything else works fine except for demister, switch to defrost if the fan goes full speed but sounds like its struggling to push air through the demister vent, its probably flap stuck, whip the glove box out( about 4 bolts i think disconect wiring and remove.
Now from passenger side foorwell you ahould be able to see all the linkages that operate the flaps, as you would expect the top one is demister flap switch heater controlls several times from auto to demist the linkage should move if not then its stuck. Try forcing ir a little as you switch to demist it should go, then lubricate and put back together. All is fine, hopefully maybe just a thought anyway been there before, good luck.

[RickT]

yeah.. do the above first to check whats going on.. before going to the ********..

RicKT

[scorpio]

Just an update to , hopefully, close this one. The local dealer did clear a lot of rubbish (leaves/dirt) from the well housing the battery (needed to remove battery first, in itself, not an easy job as battery very heavy and awkward to undo. The drainage plugs were blocked (patent Audi design with lovely opening/closing rubber exit flaps) and these were amended (with a Stanley knife!) to allow better drainage.

No immediate success, but after a couple of weeks with the engine warming/drying the wet flap motor, all seems to have returned to normal.

Thanks all for your help.

Rgds,
Scorp