HVAC AC drops to heater vent on acceleration

KRR711

MEMBER
1998 CHEVROLET LUMINA
3.1L
6 CYL
2WD
AUTOMATIC
178,000 MILES

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

5 Replies

ASEMASTER6371

MECHANIC
52,797 POSTS

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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Monday, October 1st, 2018 AT 12:54 PM

KRR711

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4 POSTS

I will check in the morning and let you know!

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Monday, October 1st, 2018 AT 1:04 PM

ASEMASTER6371

MECHANIC
52,797 POSTS

Sounds like a plan.

Roy

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Monday, October 1st, 2018 AT 1:05 PM

KRR711

MEMBER
4 POSTS

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!

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Wednesday, October 3rd, 2018 AT 1:49 PM

ASEMASTER6371