heat question

[t2933rm]

I have a 79 928, and am getting the strangest heat problem.

I get heat out of the two door vents, I get warm (but not hot) air out of the defrost vent, and I get only cold out of the two center vents and the FLOOR vents???

When I move the slider to mix air it adjusts where it is blowing, ie. put it to floor and it blows down low, put it in def and it switches to the defrost vent, ... so it seems to work.

Any Idea's?? I was not getting heat and had to add a 1/2 gallon of coolant and not I am getting the above mentioned scenario??

Help!

[928ram]

I've not had to deal with it myself as yet, but it's pretty common for the air distribution doors to stop working. It's going to be similar to chasing down elec. problems.
The system runs on vacuum; the control head is just a big multi-port vac. switch, and each door has a vac. diagphram on it (5 total??, one is in the outer cowl area). You'll likely need a Mity-Vac to make testing easier; basicall pulling hoses and checking each unit plus control head and vac. source.
I'm pretty sure I posted the schematic for the '79 here before; I'll look for it and repost it here.

[t2933rm]

thanks,
look forward for the schematic

[928ram]

Found it:

[..P]

Sheesh, I have a similar problem, but that dang schematic looks pretty much like rocket science!

P

[t2933rm]

I gave up, I put the cover on the car and I will fight this battle in the spring. I did not quite understand the schematic until I took apart the panels behind the Radio and saw all the vacuum lines now the schematic makes since, The colors help out as they are still true on my car. But today in Michigan it was 15 degrees, and a few inches of snow on the ground, which makes it toooooo cold to work in the garage

[Iggy]

Don't give up...here's a nice write-up on how to hunt down the problem:

http://members.rennlist.com/pirtle/svc_act.html