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A/C goes off

(1999 Chevrolet Monte Carlo)
in Tucson, AZ on August 25, 2010
As i accelerate at about 30 MPH the A/C stops blowing out of the dash vents & some blows out from under the dash.
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Popular Answer
of FiveStar ServiCenter on August 25, 2010
Your HVAC (heating, ventilating, air-conditioning) system air distribution is driven by engine vacuum. The fail mode (in the event of loss of vacuum) directs air to defrost and some to floor.

Engine vacuum decreases on acceleration due to throttle opening. Because of this there is a vacuum reserve canister, I believe it's a plastic ball mounted on the firewall. Check to see If that is disconnected or cracked, otherwise there is a check valve inline which may have failed.

Best of luck
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on August 25, 2010
Thanks very much. I'll check it out tonight.
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