I have 87 truck. Got the ac charged and repalced hoses, belt and dryer. The air blows strong on the floor vent but the vents in the dash not so good. Is there a cable that controls this on the ac controls or is it an electric switch behind the controls. I changed my setting on ac to max, norm, bilevel and it blows the same always. Any ideas??
The AC vents are vacuum controlled. Only the cold - hot diverter is cable controlled. Check the lines to make sure none of them are damaged or disconnected. Unless your truck is a diesel, there should be a vacuum reservoir/canister (black ball) in the engine bay on the firewall, I'd start tracing from there to make sure it didn't get disconnected from the engine. If vacuum lines check out, pull the lower piece of the main air duct off the a/c box (behind the glove box). There is a small white tab that attaches the diverter to its vacuum actuator that commonly breaks. I'm not sure this will cause the problem you are describing though, as I've had mine break and still blow through the dash vents.
