I have a 2004 Chevy Tahoe that isn't overheating but I'm only getting cold air from the heater?
The first and most basic step is to test the ratio in your cooling system. It's suppose to be 50% coolant and 50% water. If there is not enough water then there is no liquid getting hot because coolant cannot be heated. Second the thermostat might be stuck open not letting the liquid heat up.