One other "quick fix" I found. Hose pinch off pliers. Since the problem is hot air getting mixed with the cold air, my brother suggested using the hose pinch off pliers to stop the hot water from getting into the heater core. Now, this won't work if you also need refridgerant, and it surely won't work as good as fixing the problem, but it is getting me by until I have time to spend the weekend tearing my truck apart. Maybee it will work for other people too. BTW, the hose pinch off pliers are only like $5 for two of them (one smaller, one larger) at the local parts store.