Questions and Answers

Ford Taurus A/C Goes to Defrost Q. When running the ventilation of either just outside air or with the A/C on, the air blows out the vents in the dash as they should. When stepping on the accelerator, the air flow changes to the defrost mode and comes out the defroster vents for the windshield. When taking you foot off the accelerator, the air flow returns to the dash vents. Is there a vacuum problem causing this. If so, can you direct me as to what it may be? 1993 Ford Taurus GL 3.0 liter engine Automatic transmissions Manual heating and A/C Thank you, Joe

A. If the vacuum system functions normally at idle but goes to defrost during acceleration, a small leak exists in the system. The leak can be located by turning off the engine and using a hand vacuum pump/gauge to check for vacuum delay while selectively blocking off vacuum hoses.

I would start with the vacuum tank and check valve under the hood. This is the most likely location of a leak.