loose ac air flow when vehicle accelerates

Asked by Sep 11, 2016 at 01:46 PM about the 1997 GMC Jimmy

Question type: Maintenance & Repair

When I step on the gas the air flow out of the ac vents are reduced to almost nothing and it comes out defroster vents top of dash

3 Answers

86,565

Defrost is the default setting when you loose vacuum, so you have a vacuum leak somewhere in the vacuum control systems for the heater/defrost. Make sure the line is not split from the engine to the control head inside the vehicle, if that is good then your going to have to test every vacuum servo motor, supply lines and control valve for a vacuum leak. Yes it can get involved.

60,915

Most likely the vacuum check valve is bad. It's in line at the vacuum hose coming from the engine to the vacuum reserve tank on the driver's side fender. It usually looks like a little black or white disc with a vacuum hose connected to each side of it. HTH. -Jim

17,265

There is a vacuum canister mounted on your hood. It looks like a plastic ball and should have one vacuum line going to it. It helps prevent this

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