AC blows out bottom instead of vents

[Pappys84]

84 Chevy C10-been sitting up a while. Slowly cleaning and checking out systems. When set to AC , very weak air comes out the vents but the bottom floor vent blows much stronger. It does this with ac, max and the bi-level setting. Didn’t notice air out defrost. Any suggestions.
PS: truck had set up several years and rats had nested in engine compartment-some damage to wiring but i didn’t see any chewed completely apart.

 

[gmbellew]

search on hvac. there are a couple of threads that show pics of the clip that frequently breaks on the blend door and the connector rod between the two main blend doors. the glove box and the vertical duct piece need to come out and from there you should be able to see what you have.

 

[Matt69olds]

The other possibility is the vacuum switch on the back of the A/C control head, and the hose that feeds the vacuum to the servo.

 

[Blue Ox]

Like Matt said. That's exactly what mine did when the vaccum line on the firewall to the blower box broke.