I have recently noticed my defrost mode is no longer functioning. To be honest I do not know if it ever worked but I think it did. I have had the truck for a few years and half of the time it was not running because of a major engine upgrade. My orginal 360 is now a happy 360 with new eldebrock intake, cam, headers etc.

The new intake requires a repositioning of the AC compressor and I have not done that as of yet. So here is the question, with the A/C no longer functioning and the electrical and and all hoses removed, will that affect the defrost function? I have vacuum to the heat doors because I can physically move them to the open position and push the heat button and they will close. The dash vents are always open and air is moving through them but the defrost mode does not function. I have hot air at my feet and vents but can't get it up on the window and just wonder if the absence of A/C components is at the base of my problems. Any thoughts? tnx psg