[ssgharkness020147]

First of all we would need to know if he has the updated HVAC system. So, are the HVAC controls the knobs or the "sliders". If he has the knobs it is the newer system, which I can help you with. The knob system is in fact vacuum controled, my guess would be the vacuum pump is not working any longer. Does he get defrost? If he gets defrost and nothing else (he may get some A/C from the vents) the pump itself is shot. Does he have access to a vacuum guage? If so tell him to pull the white line off of the wastegate solenoid, start the truck and measure for vacuum. He should get at least 18 hg in. If the pump is shot it will probably be more like 10.