Climate Control Problems
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New User
Joined: Aug 2003
Posts: 5
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From: Arizona
Climate Control Problems
Okay, here's my problem. It just started out of nowhere. The defrost vents blow all the time. Except when the dial is in the "OFF" position. In any other position (A/C, Max A/C, Vent, Floor, Mix) only the defrost vent blows. No air is being blown through the floor vents or dash vents. I have no idea what it is. I live in Arizona where I need my A/C. Please Help!!!
---Aaron
1996 F150 XLT 4x4 5.0L
---Aaron
1996 F150 XLT 4x4 5.0L
Fleet Mechanic
Joined: Sep 2003
Posts: 1,716
Likes: 15
Look for a broken or disconnected vac line that was supposed to be feeding vacuum from the engine to the heater/AC control unit.
With no vacuum, the default airflow routing is Defrost, for safety.
There is a check valve and a vacuum storage canister, too.
With no vacuum, the default airflow routing is Defrost, for safety.
There is a check valve and a vacuum storage canister, too.
Senior User
Joined: Sep 2002
Posts: 167
Likes: 0
From: Alberta
My truck had similar problems; I found a cracked vacuum hose running in the engine compartment (passengers side) that was routed near the manifold. It is a white hose, and gets exposed to a lot of heat from the engine block, apparently other people have had problems with this same hose. I'd start by looking there; if not, start tracing all the tubing that goes to the HVAC unit...
