Heater/Defrost ??

[kenm78]

Ok my heater and fan are doing fine blowing great, but all I can get is heat from the floor and the dash outlets. Very little if any coming out of the defrost vents. While I am installing my new gauges I wanted to check the cables etc. I found that the selector for a/c, vents, floor, defrost is got what looks to be vacuum lines going to it and a 3 prong wire. I would like to get my defrost working any thoughts or ideas, or even the fix?? Thanks.

[1973GMC_1500]

Check for any lines that have come off or are cracked. I don't remember which color feeds the control. Does it switch between floor and vent or does it always come out of both?
If it switches to those but not defrost,
the actuator for defrost is right above the floor outlet (LH end of the box). If the line going to it is fine, you might need a new heater control.
You should be able to manually actuate the defrost door and possibly wedge something in where the floor heat duct bolts on.
On my '89 suburban there was enough room to stick a pencil in between the 2 pieces and that held the defrost door open enough that it would actually somewhat work.

If nothing changes when you move the selector either the heater controls need to be replaced or you're not getting vacuum to it.

[463]

fyi: you may have a object that fell in the defroster air outlets on the dash like shell casings or live rounds. i have seen this in a few trucks used by hunters.