#2isgreen

Hey everybody!
I've been having a heck of a time with the air flow from my HVAC system. 90% of the air comes out of the main vents no matter what button I have selected. For example if I have the defrost button pushed, all the air still comes out the main vents. I've confirmed I have good vaccume to the control gates, I'm wondering if the rubber bladders in them can get stiff and not allow them enough travel.

ppiggppenn

Could it be debris in the HVAC box blocking airflow? There's a real good sticky on how to break into there (just under the glove box) and clear it out.

#2isgreen

I read the stickey, that's deffinatly not the problem although it explains why the PO put black duct tape there...
I have great air flow I just can't get the air to come out of the floor or windshield vents

Jim5870

I've seen it where the various doors in the hvac box sieze up
due to rust on the shafts

#2isgreen

Alright so WD-40 and wiggle it a bunch. Sounds like a fun time. Any idea where the gate is that sends the air to the de-froster? I found the floor gate and the one over the trans hump. Any others I should look for?

ez_lle71

make sure you check the hvac control thing. the back fell off mine one day and the buttons would push thru!! it got it all sorted back correct and reglued the back back on. just a thing to check.
ez

#2isgreen

OK lets bring this one back to the table...

i got a vac gauge. my pump is pulling 30+ inches vac at the brake booster. from inside the cab i started testing one hvac control line at a time with the truck running. i think I've isolated my issue to two lines behind the glove box. the culprit seems to the the line that pulls the diaphragm that pulls the rod to operate the hvac door by the trans hump. it is red. it only has 10" vac and cannot operate the door. however if i help it by pulling on the rod manually it flops the door closed and sends my defrost air to the windshield where it should be!
the second line with a problem is the light green one that pulls the "indoor/outdoor" air control door open and closed. this line also has only 10" vac. on its own power the system can only blow "interior" air, and cannot close the door to bring in fresh air.
i inspected both lines, and the air line splitter harness thing behind the ashtray and all seems to be intact and in fine order.

this all leads me to believe that my actual hvac dash control has gone bad. I'm also open to other ideas...

Santaclaus

Have you tried checking vacuum at the back of the hvac dash control? That will tell you if the vacuum line is bad or the control is bad. It might be that the previous owner screwed up the line somehow. Mike