HVAC Vents and Vacuum
 

Hey fellas, I can't seem to figure out why my vents won't work. Only the defrost and floor seem to come on. I have done some research and have searched through threads and got some good info on what to test. I have checked the vacuum lines under the hood and they were all good. I did find that the white/grey line going to the t-case was leaking some, and so I replaced the 6 inches or so of the rubber hose that goes into the t-case plug. If I have to replace the whole section of the white/grey, or pull the glove box (line going through firewall checked out) I will.

I looked under the dash while turning the selection knob from off to vents, and the actuator with the yellow line does nothing.

Anyone have a route I should take?

Anyone have anything?

does your 4x4 work correctly? is your brakes working properly? if not it could be your vaccuum pump. to check it take the vaccuum line of the brake booster while the engine is running and stick you finger over the opening in the hose. if it sucks its not the pump and you have a leak somewhere else. ive had the vaccuum line completely unhooked from the transfer case and it didnt effect the vent operation. so if its a vaccuum problem then is either a large vaccuum hose diconnected or a vaccuum directly to the hvac system. take a look and there is a line that runs directly to the hvac directly above the coolant lines going to the heater core that runs down the passenger side of the top of the cylinder head.

The brakes and the 4x4 work as they should. I tried to blow through the vacuum line going across the firewall, as well as the line going through the firewall, and they seemed air tight. I will check the vacuum pump tomorrow. Thanks

Ok, I got the vents to work by manually moving the actuator under the dash. The actuator will stay in the down position (vents on) when I take pressure off of it. When I turn the selector dial to anything but the vents, the actuator moves as it should and changes over to the setting selected.

So, I have narrowed it down to two possible things: 1. There is not enough vacuum to start the actuator -but enough to hold it. 2. The diaphragms in the actuator are bad.

hey i'm having this same problem, but i'm pretty sure mine started after i fixed a leaking heater core.. so i'm sure i just forgot to reconnect some under-dash vacuum stuff..

my 4x4 also works.. i have hydroboost, so brakes are fine..
i suspect a vacuum leak somewhere.. i reccommend breaking out some zip ties and using it to secure any tubes that fall out of their rubber boots too easily..

gonna take apart my dash tomorrow i'll let you know if i figure it out.