My Buick Rainier vent systems has 5 vent door Actuators. The A/C runs and blows cold air out the defrost and throught he floor vents but not out the front vents of the Dash board. Which of these actuators cuts off the air going to the defrost/floor and allows it to come out the front vents.

SOURCE: 2000 Astro van - vent

The problem is a 1/8 diameter hose that runs from the front of the engine over the top and connects at the rear of engine on the drivers side. It is a vacuum hose #GM15967970 It cost about $6.22 at your GM dealer. Hope this helps Bill. My E-Mail is [email protected]
This was posted on a problem with a 2002 astro, I do believe it is the same fix. A simple vacuum hose, It is difficult to route through the engine

SOURCE: PROBLEM WHEN SELECTING THE DIRECTION FOR THE AIR

Sounds like you have a supply vacuum problem. When you lose supply vacuum to the control head it defaults to defrost.

SOURCE: Dash vents will not blow air. Defroster and floor vents blow fine.

Is it a new vehicle? I had a new vehicle that had the same problem. Answer was that the holes weren't punched out of the vent.

SOURCE: 2003 Dodge Ram 4.7, AC barely blows except for

Could be a bad recirc door housing, or a bad mode door actuator. There are not four vent actuators. I do see alot of recirc door housings break, and cause the problem you describe.

SOURCE: Air won't blow through front dash vents of my 96 Buick Park Ave

no most likely air vents are clogged