HVAC AC drops to heater vent on acceleration

1998 CHEVROLET LUMINA
178,000 MILES • 3.1L • 6 CYL • 2WD • AUTOMATIC
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I have heard variations of this question. Upon acceleration, the cold AC drops to heater vents. After stabilizing speed, the AC will go back to the upper vents. Please help. This is my only car and I have chased all the vacuum lines and all looks clean and unbroken. If I could afford the cost of repair, but I cannot find anyone here in Indianapolis to work on it. Thank you. Kenny
Oct 1, 2018 at 12:33 PM
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ASEMASTER6371
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Good afternoon.

When you were looking at the lines, did you find a big tank?

That is the tank that fails. It is supposed to store vacuum for the doors under power.

Re check the lines again.


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Oct 1, 2018 at 12:54 PM
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I will check in the morning and let you know!
Oct 1, 2018 at 1:04 PM
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ASEMASTER6371
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Sounds like a plan.

Roy
Oct 1, 2018 at 1:05 PM
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Hello Roy, sorry about the delay but I just got the car fixed. It was the vacuum reservoir on the 1998 Lumina. What happened was the mounting screw for the tank had rusted away and the tank was flopping around and pulled the hose off. By the time I actually located the tank (buried really deep under the driver's side fender well) I bought a new tank and replaced the screw and nut. Now it runs perfectly! AC does not kick out on acceleration. Thank you for sharing your skill!
Oct 3, 2018 at 1:49 PM
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ASEMASTER6371
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You are welcome.

Always glad to help.

Roy
Oct 3, 2018 at 1:50 PM