While I've been waiting for the moderators to post my other questions, I've done some more investigating. I don't think this info will help any, but here it is: If I disconnect the vent valve in the dash it still does not kick over to heater or defrost. However, if I disconnect the vent valve I can push the linkage up for the defrost and force air out the windshield defrost vents. But, like I said, it does not really help any. Because, why isn't the vacuum switching? The switch or the other possible melted vacuum valve in the engine compartment?