I just recently experienced a problem with what I think is my A/C flow damper. It's always had problems since I haven't had floor heat for a couple of years, but vent and defrost work great. Here about 3 days ago I turned the a/c on and it blew vent but then went to either floor or defrost, I'm not sure which one. I've done some research and it should be a vacuum operated damper but I'm not sure how to access it or the vacuum hose that operates it. I'll do some more searching on the truck and update when needed. Had anyone had this problem? How did you fix it? It's hot here in texas and a/c is a must

 

Alright I looked deeper and used a flashlight. I shined the light into the interior intake below the glove box. I noticed a piece of paper that appeared to have possibly fallen out of the glove box and sucked into the intake. That somewhat solves the problem. When I switch to floor, it blows out the vents which it has been doing for years. It's really started bothering me and does anyone have any input?

 

The intake you are looking at is only activated on A/C "max". That's the recirculate opening that lets the A/C system suck in cold inside air instead of outside air which would be the "normal" mode. The actuator for the "max" or "normal" mode door is under the hood over by the pass side hood hinge. In "normal" mode it sucks air in from the grille at the base of the windshield.

Those vacuum lines going to that actuator do like to rot up. I usually cut the plastic line off till I get to a good piece, and slip a piece of regular vacuum line over what's left and run it to the actuator.

In that same area by the pass side hood hinge is where the main vacuum supply from the vacuum tree goes in through the firewall to supply the whole underdash system.

 

Yeah I fixed the max a/c and normal problem. That was just trash in the interior intake. Now I'm stuck on why I don't have floor. It still blows out the vents even when it's on floor although a slight breeze comes out the floor vents

 

<p>My guess is the hinge for the deflector door/flap has broken, that flap routes air to the selected places but it can't do it if the hinge is broken. People have used piano-type of hinges from Hobby Lobby and the like.</p>

 

Or, it could be this little charmer, which is the usual problem (besides the individual vacuum motors) why a door doesn't open:

EOTZ-19B888-B .. A/C Vacuum Controlled Selector Valve Assy (Motorcraft YH-361) / Available from Ford

MSRP: $200.20 / FTE sponsor silverstatefordparts.com online price: $115.21 / Gaudin Ford - Las Vegas NV

Applications: 1980/82 F100/350 & Bronco with factory installed integral A/C

Mounts to backside of A/C/heater control panel, all the vacuum lines connect to it. When the lever is slid on the panel, this valve opens one door, closes another.

OP failed to mention what year his truck is. (sigh) / OP's "About Me" profile says 1981 F150.