Hopefully this one is easy...

This problem first showed up about a month ago. It came and went. Then it came and never went. Now the only place any air comes out of in my truck is from the windshield defrost. AC still works fine. Heater works fine... just won't blow out of the vents.

Any ideas what happened or what i can do to fix it? Is it a fuse, maybe?

Thanks!
Robert

 

May want to check the vacuum hoses behind the HVAC controls.

 

Don't bother checking behind the HVAC controls.

Inspect the small vacuum line that goes through the firewall. It is located between the battery and the firewall and is notorious for leaking due to the proximity to the fumes from the battery.

It is easy to repair using a small length of rubber vacuum hose. Just cut out the faulty area and splice it together with the rubber hose section.

Steve

 

This worked for me, I was only getting air blowing from my dash and defrost vents (warm head-cold feet) and looked into the blend door issue, here is what I found. Remove the black cover on the tranny hump, and look under the dash (way under) on the drivers side, there are 2 blend doors (that I saw) one is for the dash vents, you can see a grey foam gasket about 1/4 inch thick, I carefully stuck my finger behind this material and tested the selector **** with the engine running, I felt the door move as expected, the other is lower and closer to the output vent, it looks like a soup can with 2 vac lines connecting to the rear, I removed the vac lines and removed the 2 screw holding the unit to it's frame, the unit should dangle there, if so it's more than likely ok, connect the vac lines and test, the silver rod inside actuates the other blend door, Mine just fell out, revealing the source of the problem, I stuck my finger inside the opening and gripped the door (NOT an easy task) and rehooked the shaft to the door connector, replaced the 2 screws and now...I have warm feet!
It took 2 hours of screwing around, now that I've done it I expect it would take less than 1/2 hour to test/make this repair. (ps, I did this repair a second time, took me 30 minutes, the rod fell out again so I put a slight downward bend in it, it hasn't happened again)
Good Luck

 

oops, didn't see the "came and went" part, mine was "all of a sudden"