Newbie here!
I've got an '88 GT with about 170K miles. We had some freeze plug problems so we rebuilt the engine. Somehow, the heater core piping broke during all this, so I had to travel to distant lands behind the dash. I've reinstalled in the dash, put in a new clutch cable, a new clutch quadrant (thanks to the recommendations from the forum) and about ready to finish up behind the dash.

Last night I turned the car on (not running, though) to test the electronics before I screwed the dash in completely. I noticed the "duct selector" on the HVAC controls did not work. The fan speed worked, and the temp selector made noise as it redirected air.

Is the "duct selector" run off vacuum lines? Should it have worked with the car not running?
If someone knows, or could try it out before they start their car and let me know.

 

Can't remeber if its cable or vacuum but there is a vacuum mod. that is connected to the back of the dash that probably came unhooked. Look under the driver side dash toward the top passanger side.

 

The system is run off vaccum! You need the car running to test it. You should have had to pull a little black hose out of the firewall if you tool the box out and you have to plug that back into your vaccum tree. If you did not take it out like that, start the car up and it should work!