79corvetter

I have just finished overhaulling my AC on my 1979 Corvette L82. I have replaced all the vacum lines, Compressor, Drier, Orfice tube, Heater control Valve, evaporator coil , heater core, and all the heater/AC box seals (just about everything). Air works well.
Now my problem.
While driving my car I only get air out of the vents while just puting around. Going down the Hwy it only comes out the floor vents. if I get off the gas it will then start to blow from the vents agian. Has anyone had this problem or does someone know what I need to do to fix this?

mfendley

Have you checked the vacuum check valve and vacuum cannister? When you let off the gas, the engine vacuum increases, and the doors move to the commanded (correct) position. As you open the throttle, vacuum drops, and without an alternate source of vacuum (the cannister, along with the check valve) the doors drift to dump all the cold air to the floor.