I have a 91 s10 Blazer 4.3 vortec....I cannot seem to get the control panel to switch from the defrost & floor to the vent settings or anything else. It will not switch to A/C either...I was thinking that maybe it could be vacuum line related?? Also, (I don't know if this would have anything to do with the vacuum line) but when the vehicle is warm and you try to restart it,....I have to push the gas pedal to the floor and then it will restart. It is fuel injected, so I guess I'm grasping at strings here...please help!!
Thank you!!
Carrie

I have a hissing noise coming from the dash or steering column area...also my heater control will not switch from the defrost/floor setting. I first noticed the noise after I shut the truck off and it was quiet, but I am also now hearing it with the truck running. Please help!!
Thank you
Carrie

 

Sounds like a vacuum leak in the HVAC routing.