OK I posted about this a long time ago and thought it was the coffee can. I have now put the new heater core in all the vaccuum switches when pushed manually move so nothing is frooze up. also I can here it hiss from the hoses when pushed manually. so I don't think I have a faulty door switch. that brings me to the main switch on the dash where the vacuum hoses attach to the switch. this seem mechanical and I am not sure that can go bad. Can they? is that common? any suggestions? I seem to have mainly just defrost air when the fan is on no changes no matter where the switch is placed. I have the coffee can unbolted and I hear no leak in it at all when I put my ear up to it. This is a 74 Comet with AC
a/c heaters are defaulted to def when vac is leaking or no vac is getting to the blend doors , if the lines are disconnected at the vac switch listen for vac there if you have vac you can eliminate the source to the switch
How do I get to it? I'm working on a '77 Maverick w/ factory AC. The vacuum switch controlling the door movements seems to be bad and I found a replacement, but I cannot figure out how to get access to it and change it for the life of me.... any suggestions?
you will have to take the instrument cluster out to get to it. You will also have to pull off the little chrome knobs off the switch levers and pry the cover off to get to the three screws holding switch assembly to dash.
The plastic ends on the switch commonly break off. If you see a rubber disc with a bunch of tiny holes on the end, then yours is gone. With no vacuum or broken switch, it will only blow out the defroster.
I had to replace Tammy's is had a leak in the dash selector I could hear the leak. It wouldn't create enough vaccum to move the doors and as dennis said it defalted out the defroster. Replaced the dash selector and it fixed everything.
