Vent Door

[Doubletop]

Can anyone advise what control setting is supposed to open the door at the bottom passenger kickpanel on a 87 GMC? It doesn't seem to open on any setting. I have A/C, but it is currently inoperable.

 

[75gmck25]

That lower door will open when the A/C is on the max or recirculate setting. It also closes off the cowl intake (outside under the windshield) to about 80% so you get a small amount of outside air, but mostly inside air recirculating.

Do you have vacuum to your HVAC controls so that it switches between floor, vent and windshield?

 

[Doubletop]

Yes, it switches between floor, vent, and defrost. Just haven't gotten to start on A/C yet. Thanks for the response