HVAC system output goes to defrost and floor upon acceleration

Brett Dikeman quattro at frank.mercea.net
Wed Jul 11 23:13:11 EDT 2007

On Jul 11, 2007, at 3:47 PM, Ed Kellock wrote:

> I've seen it many times before but I've forgotten the cause and can't
> seem to find it in the archives.
> When I open the throttle to accelerate or hold speed going up a hill,
> the blower output goes to the floor and the windshield.  This is
> happening on both my Avant and my 93 V8.
> Is this as simple as a vacuum leak somewhere?

Check valve failure, or vacuum leak are my guesses.  If it's leaking  
anywhere in the passenger compartment, should be detectable at idle.

After shutting off the engine, do you get any flap movement or  
hissing punching up different buttons on the AC head?  If not, your  
system isn't holding a vacuum, at least on the type 44's you can get  
a *few* reactions from the CC unit before vacuum is exhausted.


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