I have my dash apart.
The reason is because the select switch ( the one for defrost, floor, and vent) does not actuate the doors when I change the positions. It only stays on the floor.
I know the cool-heat switch in actuated via cable and the other one is vacuum.
Where does the heater get its vacuum from to actuate the different doors? Have you ever had this issue, if so how did you fix it?
I can change the heat level and the on/off switch works perfect.
Im in phoenix and would like to figure this out so I can also use the Ac.

 

For the manual a/c controls there is one vacuum line that runs through the firewall just below where the a/c lines run through. That line goes to the intake manifold for non-turbos & to the vacuum pump on the turbo models.

For the auto a/c controls, there are two vacuum lines.

That's where it gets vacuum, but there are also vacuum lines for all the controls & ports, and if any one of those is cracked, or leaking, the system will default to floor & defrost.

 

I did check those lines. But what your saying about the default to the floor sounds like maybe my system is just sucking air. I will have to check the lines now. This sucks Im sure I will find the damaged line. Is there something I can buy to fix the leak with out removing/replacing the line?

 

It's almost always a split end of the hose at the connection. Chop it, plug back in & wind it w/ some electrical tape.

 

Well so I should have posted this earlier. I went out and followed the line and for sure there was a line that I had thought I had fixed about a year ago. Well that line was damaged. So I cut the two ends and pushed a tube into both ends to make it a single hose again. Thank you. Oh and now that I have the dash, sterio, and everything wroking I found in my back seat that I had forgot to put in a peice of duct that goes to the passengers side by the door. I am not about to tear that apart again just for that. Maybe another time.

Thanks Nismo. I should pay you for trouble shooting.

 

mine is stuck on the defroster. I live in CT and I do need heat. It still blows hot but won't change the same as yours. This could possibly explain the vacuum port on the intake manifold that has nothing plugged into it....