its a 2001 5.9l. well since im in texas and it just now got cold. I find out my heater does not work. Everything works just fine but the air that comes out of the vents is not even warm. Its ice cold. I have flushed my heater core, its got a water pump with less then 10,000 miles, newer thermostat, all hoses get hot, heater core gets hot, i have changed the control panel, made sure no air is in the system. Nothing! Like said before everything works...a/c works great and air blows great. But during the summer on a trip my a/c was leaking water into the cab and all over underneath where the heater, blower motor is. Come to find out a rag had fallen in front of the drain hole and backing the system up. I figured this has something to do with it but i cant find anything...relay...sensor...that runs the heater down there....help...