My father in law installed an aftermarker sterio in my camaro before I got the car. Cheap POS roadgear from walmart, but that is besides the point. The sterio pushes up againt the climate controls, for some reason, which causes the only vents that work are the defrost vents. Has anyone else had this problem?

 

The heater/AC controls are vacuum controlled (don't ask me why), so my guess would be that the head unit may be pinching a line or even broken through one. The controls then get stuck in the last position they were in. I'd get a real mounting kit for it (one that centers the unit), and while it's out, take a look at the vacuum lines coming out of the heater controls. There is a whole mess of hard plastic lines to check for pinches or cracks. If you find nothing there, do a search for "heater control" on the boards to for more troubleshooting tips.

Can anyone think of any other reasons for it to not work ?