91 Chevy S10 Pickup Heat Mode Selector Problem?

T

tim

New member
The mode selector doesn't work. No matter what I select, defrost, vents, etc., it just kind of blows out all of them. What should I look for..? thanks
 
It's going to help if you have another person to lend you a hand with this one. Have him/her move the inoperative selector lever while you put your head as far under the dash as you can with a flashlight. Look for the "dangling" cable that may be disconnected or for a vacuum line not in place. It could be that you have a total loss of vacuum to the HVAC control panel but I would suspect a disconnect in the mechanical cable(s). Good luck with the S10, they're a pretty tough truck.
 
Can you hear vacuum hissing inside the truck or behing the heater panel? If not, then the problem is likely under the hood. There is a vacuum hose that comes off the front of the throttle body and tees off into the passenger compartment. Best bet is to find the black ball under the hood and follow the vac hose to the tee, then check all the hoses from there. If all hoses are good, the vac port on the throttle body unit could be clogged, this was the case with my 89 s10 when I bought it at 220K miles
 
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