[V8] theoretical vacuum questions from the center of my mind.....

[Dave Saad]

I swear these cars read this list and coordinate with what to fail next...

I just had my climate control start acting weird - air would not go through the correct vents most of the time - but sometimes it did.  I replaced the vacuum control unit with a spare I had laying around and all is well.  It is probably a bad or leaky solenoid valve inside but I have not dissected it yet.  I don't know if your car uses a similar system, but if it does, this is a good place to start looking.  There is also a vacuum source hose somewhere under the hood.  It will usually have a check valve on it and maybe even some sort of reservoir.  This could have been knocked loose or broke during some service you had done?? 

Dave


On Jan 20, 2012, at 3:55 PM, Roger M. Woodbury wrote:

> I have a theoretical question about vacuum systems in these cars.  I am
> specifically working my way around a vacuum failure in my wife's 100CS, but
> I am quite certain that most Audi vacuum systems work in similar fashion.  I
> have NEVER had a vacuum failure in any of the cars which I have owned, but
> it appears that the 100CS is having a serious vaccum meltdown.  Here's what
> is happening.
> 
> Late sping, 2011:  cruise control turned off.  It just let go, and when
> reset, reset for a while and then disengaged again.  When I tried to reset
> it, no result.
> 
> At some point, and perhaps more or less the same time, we began to
> experience some unlocking/locking difficulties with the right side doors in
> the same car.  Some days the doors would lock and some days they would not.
> Some days they would not unlock with the key in the driver's door, and some
> days they would. Eventually, neither front nor rear right side door will
> lock or unloock properly with the key from the driver's side door.  nor will
> the key unlock both front and rear doors on the right side.  The left side
> appears uninvolved and both front and rear left side doors will unlock with
> the key from the driver's side.
> 
> The recirculating valve is not working properly if at all, and when it is
> cold and damp, the interior surfaces of the window fog badly.  I believe and
> have been told on this list that this is a vacuum operated flappy valve.  
> 
> Now, my questiion:  is there one pump that will provide vacuum to all of
> these points on this car?  Or are there multiple pumps?  It seems likely
> that the doors and the recirculating flap might be operated by the same
> pump/vacuum source.  I do not have a manual, and perhaps I should, but for
> now, I'll just post the question.
> 
> Replacement pumps are crazy expensive or crazy cheap and plentiful for all
> sorts of things on this car.  Any comments will be gratefully received.
> 
> Roger
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