90q20v heater valve kablooey

[Kneale Brownson]

The vacuum hose should come from the climate control controller.  It should
shut off the heater valve while the A/C is in operation.  Probably lowers
the ambient air temp in the heater core box, where the air passes through
without going directly over the heater core when heat isn't called for,
from ~200 degrees F to whatever the outside air temp is.

The version of that valve with the sensor is NLA.  You can replace the
valve with a metal version from FLAPS for around $20.  The plastic valve
without the sensor is available from most import parts sources for a
similar price.



At 04:44 PM 11/20/2006 +0000, kf21857 at comcast.net wrote:
>Hi, I am a former list member but haven't been subscribed in a while because 
>my car hasn't broken in a long time.
>
>My 90q20v with climate control has a vacuum actuated valve with a water temp 
>sensor in the heater hose a few inches from where it enters the firewall.  
>Yesterday the two halves of the valve separated while I was stopped in 
>traffic, causing the cooling system to empty itself rather quickly.  
>Fortunately I was able to find a parking spot, remove the two pieces from 
>the heater hose, unload the mountain bike I had on the roof and cycle to a 
>hardware store to find a suitable part to splice the hoses back together.
>
>Here are my questions.  I am planning a parts run to the local Audi dealer 
>to order a replacement today, but I have spent quite a bit of time searching 
>for the vacuum hose that is supposed to control this valve and it simply 
>isn't anywhere to be found.  I had noticed the valve before and wondered why 
>there was no hose going to it but had concluded that there just wasn't 
>supposed to be one.  The valve defaults to open position when there is no 
>vacuum applied so the heater works OK.  Exactly what is the function of this 
>valve and when is it supposed to be closed?  Could this be the reason why my 
>A/C has never worked worth a darn?  And where is the hose supposed to 
>originate?  The Bentley shows a schematic with all of the vacuum operated 
>controls on the heater but I haven't found anything telling me where to find 
>it.  I am guessing that it is under the dash somewhere.  Do I really need to 
>replace this thing?  Is it vitally important?  It looks rather expensive and 
>I have made a semi p
>ermanent repair by clamping a pipe nipple in place of the valve.
>thanks,
>Dave
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