Air vent door won't close

[Huw Powell]

> I just checked.  12V with the A/C on, but I don't feel any suction on the
> side where the vacuum line to the servo is located.

then track the lines back towards the T to the reservoir and the intake 
manifold via the one way valve.  also check to see if suction applied to 
the servo line actually closes the door.  it may simply be time to buy a 
couple-three of meters of new vacuum hose and replace it everywhere.

you can also check the solenoid by trying to suck through it with the AC 
set "on" and "off" - on, you should be able to draw air through it, off, 
it should be sealed.

>>>'87 4000 Q air vent door does not close when air conditioner is turned
> 
> on.
> 
>>I presume you mean the flap that blocks the fresh air intake to the
>>white plenum under the hood, making it so air is drawn over the AC
>>evaporator.
>>
>>There is an electrical switch on the heater control (I can't remember if
>>it is the "AC on/off" switch or one built onto the temp control slider)
>>that actuates a solenoid next to the plenum.  This vacuum solenoid
>>operates a servo on the side of the plenum which closes the flap.
>>
>>(earlier style type 85/81 cars have a vacuum switch right on the temp
>>control slider)
>>
>>So, first, fire the car up and set it so the flap should actuate.  Then
>>check voltage at the solenoid, vacuum supply to the solenoid, correct
>>function of solenoid.  Check the servo and flap providing your own
>>suction, and of course the condition of the various vacuum hoses.
>>
>>The vacuum "comes from" the intake manifold via a one way valve, and a
>>bit is stored off a Tee fitting in a plastic reservoir under the fender.
>>
>>This might be the same vacuum storage used for the diff lock actuation,
>>not sure about that, though.
> 

-- 
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/