Ronjoffe

Pressing the buttons on the dash control unit does not change where the air comes out. It is stuck on the lower floor outlet. Any suggestions for cause?

frosted

Control units buttons may need cleaning. Another possibility is the 'programmer', the solenoid unit at driver's side firewall that actually drives the vacuum valves. I think the control unit is a known failure point. Both are possible to open and clean without special tools.

A vacuum line leak may also be worth checking.. mine leaked at a junction below the glovebox.

Ronjoffe

drcook

1996's have a one year, known problem. in the vacuum box, GM, for some dumbass reason, decided to use rubber **** over hard plastic nipples. the rubber sucks shut from the vacuum, defaulting to defrost and floor.

My car has the same issue.

Read this:

https://www.corvetteforum.com/forums...l-problem.html

If this is your issue, you can insert thin wall brass tubes in to keep the rubber from collapsing. Might talk about that in the above link, I don't remember, been a while since I read it.

This is a project coming up for me also, as well as cleaning the contact points, possibly having the head rebuilt. If it gets hot outside, it doesn't want to command the A/C to turn on without either turning the car off and on, or undoing the battery. I spose I could locate the fuse and pull it.

bigtoys

FWIW, I am having a similar problem with my '95. When I first got the car, air would come out of the defrost vents for about 2 minutes before switching over to the dash vents. eventually it stopped changing over altogether. I even resorted to making a deflector for the dashboard that would re-direct some of the cold air from the defrost vents into the cabin. A bit "rigged", but I can live with it until it cools off enough down here to try fixing the vaccum connections.