Hey guys I've got a major heat problem in my car, it only pushes out luke warm air inside the car. I've already done a coolant flush, a thermostat (which was broken but didn't fix the inside heat problem) and recently a muriatic acid flush directly through the heater core. The last thing I can think of is that door that controls the amount of heat, the control inside the cab is stuck or something. I really don't want to have to take my dash apart but it looks like it's the only thing left to do. Any ideas?