A/C question

Cheri DeMonico

Asked by Nov 12, 2015 at 05:33 PM about the 1988 Chevrolet Corvette Coupe

Question type: Maintenance & Repair

Had a whole new system (compressor\clutch, evaporator, lines, dryer accumulator, expansion device, Freon put in except for the condensing unit, have cold air blowing BUT when you step on the accelerator and only when you use the accelerator the air starts blowing in warm, but then let off the accelerator the air blows in cold again.   Has anyone had this issue and know exactly what I need to do or what could be causing the warm air coming in?

2 Answers


There is what they call a WOT system in the A/C circuit, it cuts off the A/C when you accelerate faster than normal, so if you just ease into the throttle it should not activate the cutoff. As far as the warm air, you could have a vacuum leak in the heater controls or servos or a leak in the blend door seals that is allowing warm air from the heater core side of the unit into the A/C side, and when the A/C is cycled off you feel the warm air. HTH

2 out of 2 people think this is helpful.

There's supposed to be a check valve in the vacuum line coming from the intake manifold to the climate control panel. In addition you should have a vacuum reserve tank in the system as well. If either or both are missing you'll have temperature and possibly mode fluctuations while accelerating and decelerating. Intake manifold is highest at idle. When you step on the gas, intake manifold vacuum decreases as the engine speeds up. Normally GMs are set up that vacuum provides a/c. Is this a manual system or automatic climate (temp) control? If it's an automatic system the check valve is probably inside of the programmer under the dash behind the glove box. HTH. -Jim

2 out of 2 people think this is helpful.

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