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Re: A/C dies off when turbo kicks in & vice versa 740-760 89

posted by  someone claiming to be Tom LeStrange on  Tue Jun 23 02:35 CST 1998 [RELATED]

ICQ>

Chris,

My vote is for a faulty check valve or a leak or disconnect in the vacuum storage canister. Any A/C vehicle I have ever worked on had a vacuum canister with a check valve between it and the manifold vacuum source. This would provide a constant high vacuum to the A/C vacuum valves that control the dampers in the system even though the manifold vacuum decreased when accelerating or changes to pressure as in a turbo system. I have never worked on a Volvo A/C system, but I can't believe they are any different. The best way to check the system is to use a vacuum gage at the tank (when you find it). Connect the gage in the line and see if the vacuum remains constant when you rev the engine. The other way is to find the check valve and test it. You should be able to blow through it only in one direction. Also check vacuum line condition and listen for vacuum leaks. One other test is to actuate the A/C buttons/levers shortly after turning the ignition off. If there is any vacuum storage you should be able to make the dampers move several times until the vacuum is depleated.

Good luck,

Tom





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