I've had my '96 LT4 for just over a year and have read everything I could find on the car. Somewhere in my reading I remember a statement that indicated if no AC was coming out of the dash vents it was an indication something expensive was about to give up. I can't find the refference again and I'm not getting any output from my dash vent on heat or AC. I have the electronic climate control and it does heat and cool the car and I'm picking up no faults on the OBD II diognostics. Can anyone help me remember what unit was failing that would cause this condition. Everything else..blower,temp select, fan select all seem to be working fine.

I'm GUESSING you may be talking about the programmer ?? I've got to ask though--when you push defrost or the floor vent buttons--do they still work correctly?

Vaughn, I went out and tried it today (61degF) and the defrost and floor vents work seperately and together. With the car fully warmed up and pushed the button for floor and dash about 90% of the heat came from the floor and I was still getting heat from the defrost. A very SLIGHT flow of heat came from the dash vents with the temp set on 82 and fan on 8. The floor and defrost vents flow with any buttons pushed. I have tried the same process when the temp outside was in the 90's with same results. Programmer sounds familiar..can you tell me more about it. I have the factory shop manuals, Chilton, Haynes and numerous magazine articles to ref. I just did the Optispark and waterpump last month and the car runs about 20deg cooler now. When I took off the injector cover on the left side a vacume device was broken loose and I replaced it. Two hoses came into the device and an elbow went into the intake. Thanks for your time and consideration.  Dave

The programmer is behind the inst. and to the right towards the center of the dash--vacuum ports (inside the programmer)which are controlled electrically via the control head---allow vacuum to flow to servos which control doors-that when open allow air flow to defrost--floor or dash vents depending on the button which is pushed.

Thanks Vaughn, I'll continue to check it out.