where is the ac vacuum check valve for a 1996 explorer located?
Sounds like a bad HVAC Actuator under the dash if all you have is defrost.
ac woks fine but only when speeding up the air would divert to the defrost vents...then goes back to normal after maybe 30 seconds, sometimes up to a minute...
Well then the check valve is a possibility, sounds more like a small vacuum leak somewhere since you know everything does work. Should inspect all vacuum lines on the engine. There is a separate HVAC Defrost Mode Door Actuator that works off of vacuum from the engine. Inspect the vacuum line running to it, if there is a check valve in that line, and it is bad, it could cause this problem since it only allows vacuum to flow in one direction. The reservoir for air pressure would be the Actuator itself, keeping it in the proper position as you accelerate.
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