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Corvette, 1985, lost vacuum to A/C control switch: need vacuum diagram and/or any help I can get...fan is OK, just blows out of all vents at one time.

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  • Anonymous Mar 17, 2014

    1985 corvette cruise works fine vents wont change over stays on defrost all the time

  • Anonymous Mar 27, 2014

    windshield wiper system

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Look for a vacuum pod or tank under the hood. this is most likely where the interior vacuum controls get the vacuum. Does the pod have a line that connects to the intake manifold, or the brake booster? It should., if not find missing vacuum line and repair. Follow the other vacuum line from the pod to the interior, (it is important to find the line going to the interior, as there may be more than one at the pod) is it connected to the controls? it should be. Here is a simplified verbal schematic... vacuum from engine to pod, vacuum from pod to vacuum controlled devices. GM often color codes the interior vacuum lines and that makes them easier to follow under the dash.



Posted on Sep 21, 2008

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I have a 2003 Ford F-150 FX4 5.4 and the AC only blows out of the defrost and help


Dustin, Sound like vacuum loss to position switch. Defrost is the default position when vacuum is lost in vent control system. Check any and all vacuum lines and connections under hood first, especially any that run through firewall. Check the attached links,instruction and guides, Good luck
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