Air Conditioning problem
1996 Volvo 960 6 cyl Two Wheel Drive Automatic 135110 miles
A/C cool air works perfect on all dash outlets until engine is under load as in passing or climbing hill. Then all dash vents loose air flow and no air flow anywhere but you can hear blower working fine at all speeds. After releasing gas pedal and normal driving, all air vent start to work blew cold air again, until next time.I know this unit has 4 Vac. Motors that a controllling air flow. How do I correct this condition. Thanks. Tchena.
The vents are run by vacuum from the engine. When under a load, the vacuum in the engine's intake drops. At that point is when you loose your vents. That tells me there is a vacuum leak either from the engine to the inside of the car or under the dash. With no leak, the system can handle a drop in vacuum from the engine. With an additional loss (leak) the vents can't stay in the position you want.
In this case, you are looking for a vacuum leak either under the hood or the dash. Many times with the engine running, you will hear a slight hissing noise that will help locate the leak.