I decided to pull the vacuum line to the heater control valve and plug it. After that I had instant heat, and the control module worked normally, cold when in cold position and hot when in hot. Obviously the control valve is not being told to open the valve. Any clues why this is? Or can I just leave the vacuum line plugged?

 

Bump...

By the way I finally got a NFS Porsche CD today, so I'm in on the next game..

 

I am similarly challenged with heater controls, i read on an archive that the pins connecting the controls on the dash unit get corroded and cleaning them solves a lot of problems.

 

I think the control is working, because it is controlling hot and cold when I got that vacuum line pulled. Unless that control module controls the vacuum to the valve? ANYBODY??

 

stolarzj,

I have (had) the exact same problem: no heat. Mine just started a few weeks ago, and I've been ignoring it. It's just getting colder here, now, and I can't ignore it anymore! I checked the heater clips, and they're fine. I bled the cooling system, and it's fine. I'm fairly sure the thermostat is fine. It was just replaced last November. After reading your post, I also decided to disconnect the the vacuum line to the heater valve. Instantly, I have heat again! I'm also baffled by this. Everything seems to be working properly. Thank you for posting your problem, and helping me with mine. I'm sure this isn't supposed to be a permanent fix, but since everything is working properly now, I'm happy. Hopefully someone can figure out and offer a solution. But, until then, I have heat again!!

Also, I noticed at least a 50 horsepower gain. (kidding, of course)

 

Don't suppose your vacuum hoses were off at some point. Mine were and my theory here is I have the hose for the control valve plugged into the wrong place. I just can't figure out how the engine with constant vacuum when it's running is suppose to open and close that valve, it has to have no vacuum to open the valve.

 

I think your theory is correct (stolarzj). The vacuum lines were disconnected last November, when the timing belts broke (my fault for not replacing for over 100,000 miles!), and major work was performed by a non-Porsche shop. I noticed, probably late this summer, that one of the vacuum lines was not connected. I connected it to the nearest hose, which seemed to make sense. It was weeks, possibly months, after that the first time I tried to use the heat, and it didn't work. Disconnecting the same hose, which went to the heater valve, is allowing the heat to work. It makes me wonder what else wasn't put back together correctly. (They also forgot to torque the crankshaft pulley bolt to 154 lbs, which resulted in the car having absolutely no oil pressure. They told me then the car was too old, and not worth fixing. It's been running fine since I bought a torque wrench, and torqued the bolt myself!) Anyway, it may be necessary to find a vacuum hose diagram somewhere, to see the correct routing. In the meantime, I'm happy to have heat, the heat control, and everything (seemingly) working properly. Hopefully someone will have, or know where to get access to, a diagram.

 

There is a vacuum hose diagram on the passenger side fender, but I was having a hard time making sense of it. I think I will dig around more tonight..