Problem Description and Possible Solution
The AC/heater (HVAC) system may unexpectedly switch to the defrost mode when accelerating. This system is operated by engine vacuum and should be inspected for any vacuum leaks if this problem develops. There is also a revised vacuum check valve available to address this concern.
Average mileage: 162,625 (100,000–280,000)
22 people reported this problem
Dash vents blow fine normally but under acceleration the unit switches to defroster vent. My mechanic said there is an actuator valve that can get installed somewhere (I think he installed it in engine compartment in the middle of some accessible vacuum line) to at least control the flow vents (floor, dash, defrost) and it does work - but under acceleration, it still blasts thru the defrost vents and when I let off the gas pedal, it always returns to the dash vents. I can live with this but it is annoying.
Same here, AC blows fine at idle, once accelerating, goes to defrost.