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Help!!!!! I have done everything i can think of! I have a 79 corvette. I cannot get the vacuum selector valve to select between air cond, vent, or defroster. I have tried three different selector switchs, bought a whole new selector assembly, replaced and checked the water shut off switch, replaced all the vacuum hoses and connected the hoses directly to the vacuum selector valve and nothing works. When i connect the main vacumm hose directly to any seperate component using a bypass hose they work great!, then when i hooked them up directly to the contral valve i get nothing, but air blowing out of the heater duct. the water bypass shut off seems to be working because when i select between hot and cold it works regardless of the position of the upper selection switch. Any suggestions? Have I missed something simple? I losing precious time i could be using checking out the babes section.
 

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As part of an engine bay clean up....(which included a new motor too:laughing:)... I also replaced all the vac hoses under the hood. It's easy to get the hoses crossed up. Just saying... check them again! I had my wiper fluid, headlight and heat hose vacuum lines all switch around.:surprised Nothing worked but it was late November last year so I didn't worry too much about it. I took a fresh look at the line connections again last month just for kicks and I figured out the problem. I too wasn't getting any switching between def, floor and vents. I just had the lines connection hosed up...no pun intended.

GOOD THING I didn't put any fluid in the washer reservior as I never used it any. If I would have...... I probably would have sucked a gallon of wiper fluid right into my intake by accident!

DOUGH! :lookinup::smack:WTF:nuts::crazy:
:laughing:
 

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Check the vacuum actuator return springs under the dash, right side. When I first got my 78 A/C running, it would only blow hot air, until I stretched the return spring on the actuator, the spring had a little surface rust on the coils preventing it from stretching, thus preventing the hot/cold air diverter from opening to allow cold air in.

Free your spring and cold air will follow.:thumbsup:
 
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