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HVAC vacuum issues w heater valve, throwing hot air at high RPMs 700 1991

Hvac vacuum question. 91 745 Regina . Bought car w busted heater core, and heater core plumbing bypassed and vacuum lines open. Replaced heater core and got plumbing and heat valve hooked up. ** The problem is a vacuum issue w heater valve. When driving at low Rpms w controls at coolest(blue) setting cool air blows through vents as normal . When driving on highway or at revving Rpms the damn thing blows HOT air through vents at cool setting. Great for winter, sucks for summer. What's up w that? Possible Vacuum issue elsewhere drawing vacuum away from heater valve. All interior vent flaps work correctly. I bought an A valve from IPd so I know it's a correct valve.all hoses are connected and I don't see any cracks or rub breaks in lines. Is valve normal position open or closed? Any ideas guys?
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1990 240DL red, 2004 V70 2.5t






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New HVAC vacuum issues w heater valve, throwing hot air at high RPMs [700][1991]
posted by  Mandomex  on Wed Jun 17 11:10 CST 2015 >


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