hissing coming from heater and ac controls.

[cowman79]

I have noticed that when I turn my truck off and the heater ac control is in the off position I hear a vacuum leak. Everything seems to still work but the hissing is kind of annoying when I shut the truck off. If I change the position from anything other than off it quits making noise and the door start moving like normal. I was wondering if anyone has a vacuum diagram for the heat and ac controls for my 94 truck. I even noticed today that it was making the noise when the truck was running. Does anyone have a suggestion before I go tearing my dash apart.

 

['94IDITurbo7.3]

mine does that when the engine is off and you move the hvac controls. does not move my vac gauge in the truck though. i don't notice it while the engine is running though.

 

[cowman79]

Mine only does it when the controls are in the off position. That is what is the interesting part. I can understand it making noise when moving the controls around.

 

['94IDITurbo7.3]

hmmmm. mine doesn't do that. i would say you got a good vac leak.

 

[international]

Snake?

 

[cowman79]

I guess I had better check for snakes tomorrow.