Questions and Answers

Ford Mustang Stuck On Defrost Q. My A/C stopped blowing through the A/C vents now will only blow through defroster vent. Worked fine till now. The only position that works is Off. How do I fix this? 1993 Ford Mustang 2.3 liter 4 cylinder Automatic transmission 93,000 miles P/S, A/C, Cruise control

A. The HVAC system in your car is vacuum operated. When vacuum is lost, the system defaults to the Defrost mode.

There is a vacuum tank under the hood that stores vacuum for the HVAC system. What you need to do is trace the vacuum lines to the intake manifold and the HVAC mode switch and make sure all the connections are properly attached. Also check the vacuum tank for cracks and the check valve, if equipped, is working properly.

Ford Vacuum Tanks