^^^ new product Ken?

 

You can actually see the recirculation flap from the footwell. Use a flashlight and look up thru the plastic grille. If the grille is blocked, you have outside air coming in; if you can see thru the grille, the flap is open and you will get recirculated air.

 

Wally, much appreciated.

 

Hi there,
I have an newly aquired -87 S4. Just driven about 1000 miles yet. I expirience this slapping noise from a flap in the dashboard at the passenger side.
Not related to hitting bumps and it is not related to any specific adjustment of either the heat or the airstream adjusters.
It happens randomly under normal driving, say once or twice on a 10 mile trip. When it slaps its more often heard as three or four "back and forth" slaps times than just one slap only.
I can not say for sure if it is in the upper or lower part of the right hand side dashboard, its just inside there somewhere.
When i regulate the airstream this appears to work fine between "windshield & footwell".
My AC is not working, and the drive belt has been removed from the pump many years ago.

I sometimes hear a "vacuum sound" inside there but it seems not related to the slapping. I wonder if this hissing sound at times is because a vacuum-line has come off left a flap loose to slap at its own will in the airstream. What do you think, will this vaccum-line be accessible without removing the whole assembly ?

 

read this

https://www.google.com/url?sa=t&rct=...46471029,d.aWc

At the top of the page find tips and links then go to Wallys HVAC system^^^

FWIW the reason the flap is working when the key is on is because,
the solenoids are energized with the key turned on,
this will set the solenoids to what ever is selected on the HVAC head,
and if the HVAC system is turned on and if there is vacuum in the reservoir

To test the fresh air flap in the blower box above the CE panel.
Open the hood remove the cowling find the blue vacuum line and plug a mytivac into it,
then pull a vacuum see if it holds.

 

Thanks Mrmerlin !
I will look at this link. In the mean time i have found a thread describing my problem in detail with some fixes so with both i will hopefully manage