Subject: Re: Hot Air Coming from Dash Vents !!!
From: DCBURROWS@aol.com
Date: Fri, 1 Oct 1999 22:45:10 EDT
X-Message-Number: 57

One cause of hot air always coming through the vents is a malfunctioning 
heater control valve. This can be found on the passenger side firewall just 
under the air filter housing. Remove both the upper and lower halves of the 
housing and observe the plastic valve with the heat slider on the A/C control 
head all the way to the left and then with the slider all the way to the 
right watching the actuating arm from the vacuum diaphragm. If it doesn't 
move then disconnect the small vacuum hose from the diaphragm and, using a 
piece of hose, suck on it, (or use a vacuum tester) and see if that makes the 
valve work. If it does actuate then the diaphragm is OK and there is a 
problem in the vacuum control system. If it actuates with the slider position 
then the coolant portion of the valve is probably leaking hot water through 
to the heater core. I don't remember if vacuum opens the valve or closes it 
but do whichever closes the valve and run the fan with the engine on to see 
if the air coming out of the vents gradually gets cool or cold. If it 
doesn't, then the valve is probably defective. If you buy a Volkswagen heater 
valve it might be cheaper than the Porsche one.  Good Luck.

Don Burrows
87 S4, A/T
dcburrows @aol.com