Sara ... 6/15/2010
1995 Buick Park Avenue Ultra 6 Cyl 3.8L
Body & Interior
Air conditioner will switch from vent to windshield blower on its own
AC is working, but cold air will blow out windshield (defroster vent) and not vents on dash. Also, cold air on drivers side, hot air continually on passenger side - help
You have a vacuum leak in the vacuum supply line at or near the vacuum storage canister which is a tank mounted just to the right of the master cylinder / brake booster. The tank could also be leaking vacuum. To explain why your symptom happens would be too much rambling, but the cause is a vacuum leak 4 sure.