Does any one have the vac line routing scematic for a 85' Im having trouble with very low volume of air flow in the ducts in the dash.the control is on max ac and the fan on high, a lot of the air is coming out of the the defrost vent! I checked the coil for leaves and it is clean. I pulled the resistor plate and there is a good flow blowing out there. I also noticed the door in the duct in the fire wall what position should this be in when the air is on? I was wondering if there is a vac leak some where. the vac tube thatis hooked to the engine goes into the wire loom but then where does it go? thanks for the help!

 

All GM's suck the defroster door shut except when defrost is requested. No vacuum or weak vacuum will keep it open and all a/c, heat, vent etc will blow through the defroster ducts. Trace the vacuum source from the right rear side of the intake plenum, towards the drivers side and then past the left side of the distributor. There it splits into two lines through a check valve. One goes through the firewall to the dash control (manual air) or to the programmer (electronic air). The other line goes to the vacuum tank in the left headlight well (sometimes it's easier to trace the line by following it from the tank along the left inner fender - it will split off to the cruise solenoid, but the other side goes to the check valve). Verify that there is vacuum at each port on the check valve. If so and what little you can see of the line to the firewall looks ok, you need to pull the cluster panel and then the center panel so that you can unbolt the dash control to verify that vacuum is getting to it (manual air); or remove the hush panel on the driver's side and access the programmer above the accelerator to verify it's getting vacuum (electronic air). If vacuum is ok, you need to check vacuum at the solenoid that controls the defroster door. It's on the left most side of the heater plenum above the accelerator. The vacuum lines should be red and tan. As I remember red should have vacuum at all times except for defrost and tan in the bi-level position only, the important thing is vacuum is getting through to the side connected to the door in all positions except defrost.

 

Thanks for the help,that was a great help!