My temp controls work on the ac unit, but if I push vent, defrost, heat, whatever, the air always comes from the defrost vents. What do I need to check? All plugs are tight, so I assum its a vacuum line, but where do I check it?
Thanks in advance!

86 Dodge Ram D150

 

There's a black or gray line tied on to the intake runner behind the carb that's the source. This'll be a little hard to diagnose with out a hand vacuum pump.
Pull the glove box and move the linkage manually on the vac. pot, also one right above the gas pedal. If they move freely, you'll have to vac. chk. the pots and lines. If you have vac. from the mtr to the control, and no leaks,the doors move freely, replace the control. Sometimes a pencil or some such can fall down the defroster vents and jam the defrost door.

 

Mine does smetrhing similar to this. Everytime you push ehat, defrost, vent th air comes out the vents, then slowly switches to the proper thing. But pushing vent, it starts in defrost and slowly moves to vent. What could that be. And what does the heat button do anyway? Pushing it seems to not do anythng. Where does the air come from if you push that option?

 

Comes out at the center floorboard. The control head has a rubber gasket inside with various holes in it, pushing a button covers or vents selected holes. The vacuum available is miniscule,due to the small size of the supply line from the mtr.Doesn't take much of a leak to slow or disable the system. Do the above checks.

 

I have a temporary fix.
I pulled the glove box and found the actuators for the different settings. I moved the metal pole to a position where I'm getting some air out of the vents and some at the top as well for defrost. Then locked it in place with a small clamp. When I get more time, I'll take it to someone who can measure the vaccuum for me, but this will work for now.