Picked through the FAQ thread (awesome btw) but having lingering issues.

1982 F150 XLT 302 w/ factory air

Issue: only getting air through cab registers. No air through defrost or floor when selected. I get heat with that control and it looks like that door is controlled via a cable which I checked when I pulled the heater core panel off. A/C works and kicks on appropriately in MAX, AC, MIX and DEFROST. With the heater core panel off and truck running I moved the selector but saw no movement from the other door. Popped the hood and looked in the upper left area by the heater core hoses. There was no vacuum to the motor which I assume is the recirc air door. Also a hose going through the firewall which I assume is the source vacuum for the HVAC selector switch.



I ran a line from the check valve to the motor to see if it would operate the motor and it did. There was no line going there and a vacuum cap installed on that end of the check valve. I was able to fit another vacuum hose over the stub of a hose remaining (vacuum source?) and used a t-connector off the check valve to get vacuum to both the recirc motor (?) and the source hose (?). Now when I select FLOOR, MIX, or DEFROST a door to the left of the blend door (visible with the heater core panel off, on the left) moves but doesn't look like it seals right, almost looks cocked to the side a bit. Also this motor is now moving:



Even though these are all moving now I still only get air through the registers. I buttoned everything up last night as it was getting dark. Hopped in the truck with the family to go get a Christmas tree and it ran terrible and died a couple of times so limped it back home. I'm assuming I messed something up with the vacuum and will probably put everything back the way it was until I figure this out. I'm thinking it's pulling too much vacuum and somehow messing with the carb/distributor. Any thoughts appreciated!

 

Take a look here:

https://www.ford-trucks.com/forums/1...oor-hinge.html


Specifically, see the third paragraph. It tells how to determine if the hinge has broken for the vent door.

The thirteenth paragraph describes how to temporarily block off the passage to the vents so you can have your defroster back. That should buy some time until you can do the repair.

If the vent door hinge has failed but you don't want to fabricate a replacement, post #6 has a link to buy an original style door with plastic hinge.

 

 

 

 

Ooh, be careful. Did the rough running begin only after you messed with the vacuum lines? If so, return them to the original condition for now and see if the engine behaves itself. Don't go inadvertently creating new problems, such as if you were to misroute one of the new vacuum lines. Fix one thing at a time. Once you get the engine back to normal, then confirm if the vent door hinge has failed, as previously described.

If the engine still acts up with the vacuum lines back to "normal", don't despair. Maybe you do have a vacuum leak, either in a line or at an actuator. Try a couple of things:

1) Switch the HVAC mode selector to OFF. This shuts off vacuum to most of the system except the recirc actuator. If the engine now behaves, the vacuum leak was in one of the other actuators or associated lines.

2) If no help, disconnect the vacuum line feeding the entire HVAC system. I think it's going to be connected to the Christmas tree at the back of the engine's intake manifold. Cap the fitting where the line was removed. If the engine now behaves, the leak was in the HVAC control panel, the recirc actuator, or the associated line.