1987 944T..

So I honestly don't know if it worked when I bought the car because I had never tried it until now. I checked the heater supports and both clips are in place as they should be but when I move the temperature **** back and forth, the rods aren't moving at all (zero). Should they? I'm not sure where my problem lies but am willing to investigate if you guys throw out some ideas! I looked up and down the engine bay really good to see if I had a vacuum leak somewhere and even tried spraying wd40 in some spots where I thought it might be but I didnt find a leak. I also made sure my coolant system was pressurized correctly as to not have air pockets. Outside of that I don't know what to try.. thanks in advance...

Oh, and all other components of climate control work great (a/c, recirc, diff. vents, etc). its just the heat that doesnt work!

 

Here is a helpful guide if you haven't seen it:

http://www.clarks-garage.com/pdf-manual/hvac-01.pdf

It's good that you checked the linkages, although broken ones would theoretically lead to a full heat condition. Your temperature control unit (thing with all the controls) could be bad however I would check other things first... Yes, i would think that turing the temp control should move the linkages. Having said that, there are a bunch of temp sensors feeding that system that may be faulting it.

Either way, switch from cold to hot while shining a flashlight down behind the engine by the firewall. You should see the heater valve (right above the bellhousing) actuate when you change temps. If nothing happens when you do that, pinch the vacuum line going to it and it should open if it is okay. Once you know the heater valve is operating fine (both the valve and the controls switching its position) you can move on to other checks. One step at a time.

 

thanks, yes i have read the pdf link you posted.

i will give this test with the heater valve thing a try tonight when i get home. how hard is it to see the valve from the top of the engine bay? anyone have a picture? just so i know what to look for.. thanks!

 

Here you go:

http://944time.com/porsche/944heatercontrol.php

Look down right behind the oil fill cap and you will see it. It has a little linkage arm which you will see move when it is opening/closing the valve.

 

Ok, the valve does not operate when turning temperature knobback and forth.

But when i disconnect it from the vacuum i do see the lever move to the passenger side of thecar and then back to the drivers side when i reconnect vacuum...Next step?

 

Okay, at least you know the heater valve is operational.... but that is a different issue.

Going back to your earlier mention of the flap linkages, yes they should move when you adjust the temperature ****. However, diagnosing the issue there will be more complex.

If it were me, I'd disconnect and plug the vacuum hose going to the heater valve and hope the flaps are in the right position to give you heat.

See what happens.

 

Ill try that for now so I won't get cold haha.

But as far as addressing the temp ****.. do you think that whole hvac control unit should be repalced? something like this one:

http://www.ebay.com/itm/PORSCHE-HVAC...item19c95030e7

Or should I further diagnose the problem first? If so, what's next?

 

It's possible that the unit has gone bad. Like I said diagnosing its functionality will be much more complex since there a number of things interacting to make those flaps move (i.e. there are three temp sensors (interior, outside, mix) feeding the unit which it uses to try and maintain a certain temperature). I do not know for certain how to check them.

You could start by checking the motor for the flap linkages. Keep in mind that there are three (baffle/temp, defrost, footwell). The excerpt below is from the factory workshop manual. You could try and connect 12V source power across terminals 4 and 5 to see if you get any movement. If they are truly at the cold position it sounds like the motor would be at the end of its range anyway, so I am assuming if you reverse the polarity it will spin backwards(?).

 

Cool I will try this and see what happens

 

If that motor is bad, where can I buy a replacement?

 

Well, a quick search at Pelican comes up with $305 so I wouldn't consider new an option. Try searching '944 heat' on eBay.

 

tried this morning and couldnt find anything

i found a hvac control unit for 85 shipped, went ahead and bought it. easy test to see if its the culprit.
http://www.ebay.com/itm/110751658215...84.m1497.l2649

 

didnt fix it. still cold... anyone!?

 

Have you tried unhooking the linkage? Mine popped off once, and it took me a while to realize that it gave full heat all the time.

Getting full heat doing this may point you to a controller/senor as opposed to all the flaps/controls working, but no hot coolant flowing through the system. It is also getting cold outside, and getting heat one way or another may be more important right now!

 

not a bad idea.. but i really want to figure out the source of the problem and fix it! but thanks, i might do that for a quick fix.