Okay So I've gotten it to pass smog, fixed the power steering fluid leak, replaced the power window switches, installed a stereo and now I'm working my way up the dash; next stop, HVAC.

Basically the whole panel is completely non-responsive, no fan, no change when I move the sliders, no AC pump engagement when I push the AC switch.

This wouldn't be that much of a problem if it wasn't for the fact that the heat appears to be stuck in the on position, no matter where I set the temp control there's always heat coming through the vents. This was actually kind of pleasant a few months ago when it was 30 degrees in the morning but now that summer is happening I need to do something about it.

I assume I'm going to have to rip the dash off and start troubleshooting it with a multimeter and I'm totally comfortable with that but I figured I would ask you guys first in case there's some easy stuff I can try.

Also I was wondering if anybody has ever done a heater core bypass and if that's something I should be considering as a quick fix?

Thanks in advance for the wisdom!

[edit]
I should probably mention that I have already checked all the fuses

 

Replace the hot water valve for the heater core:
http://jenniskens.livedsl.nl/Technic...4/MyTip431.htm

If the system blows hot air high fall all the time:
http://www.autoatlanta.com/porsche-p...section=809-05 #37

 

I will deffinitly take a look at that valve.
However it's not that the system BLOWS hot air, it doesn't blow at all. There's literally zero response from any of the HVAC controls.
When the car is in motion there's some hot air that comes through the vents but no fan.

 

The default when everything fails is that you get heat - and that is what you have. When you check fuses - test them electrically, not visually. Replace the blower relay and the X bus relay. If nothing obvious remove the head unit and make sure it and the blower switch are plugged in properly (2 separate plugs. See what you find. These are all easy to do. Leave the hot water valve for now - it may well work fine - too soon to tell.

 

Thanks, that gives me some things to try. Any reason I couldn't just temporarily zip-tie the hot water valve closed for now though? It's really brutal driving in 90 degree weather with the heat on.

 

That will work. It's what the PO did on my '84. I now have replaced that valve with the one the is in the link Speedtoys posted.

 

Yes no reason not to do that to start out - it won't do any harm.

Alan

 

Put the bottom slider on defrost and see if the fan works......AC switch can also be checked to see if it works in defrost position. If blower works in defrost then blower fan is ok......check fuse 17 and relay XII....if still no blower then fan may be toast......if fan works go to anti freeze relay in fan scuttle under the windshield...should have 12v on both sides and compressor "should" be running.....if not go to pressure switch on side of condensor, should have 12v on both sides....if you have 12v and compressor still no run then may be bad clutch, bad compressor or broken wire from pressure switch to clutch. If you only have 12v on one side of the pressure switch jumper the switch....if compressor runs you are low on freon....