stans

I have a 1991 corvette with vent problems. When air conditioner is on, the air comes out the floor and defrost vents, very little comes out of the dash vents. Any ideas?????

SunCr

Could be a couple or more things including a worn out seal in the air distribution duct work which is accessed by removing the top pad. With a/c, there should be a small amount of air to the floor (to cool it) and the Defrost Vents (to keep it from fogging over). If it has a Electronic Air, there is also a purge function on start up that directs air to the floor to keep residual moisture from fogging up the windshield and a problem with any of these functions would be in the Controls.

How the duct work directs the air is controlled by vacuum actuated solenoids that are mounted on the left side of the Heater Box to the right of the accelerator. You will have to remove the Driver's side lower pad or hush panel to access and before you do any testing, you might feel around both lower sides to see if there is air flow which would indicate a problem with the duct work seals. For testing the Solenoids, GM usually has a Blue hose for the a/c vent but I'd remove all of the hoses first and use a vacuum pump on each solenoid to see what happens to air flow. If they work, the problem is in the vacuum source and that will depend on whether it has Electronic or Manual Air. If one doesn't work, it needs a new Solenoid which I think is still available through a Dealer.

Cliff Harris

There is a vacuum check valve next to the distributor on the driver's side that supplies vacuum to the HVAC system in the cabin. Sometimes that check valve fails and you get no vacuum inside. Available at any auto parts store for less than $5, so it's worth replacing just to see if that is the problem: