This vehicle, equipped with a 4.6L, auto trans, gets to normal operating temp however no or very little heat even with fan at high speed setting. The heat range selector **** is not rounded off. I am clueless at this point and suffering each morning on the drive to work since the temp has fallen into the low 40s. Please provide guidance if at all possible.

 

You either have a plugged heater core, or a bad temperature blend door actator.

 

Thanks wheelsup68, can you provide any further assistance as to how I might proceed in determining which one is causing the problem?

 

You might also check to make sure your coolant level is okay. As for testing heater core circulation you need to locate the inlet and outlet hoses at firewall. Using an infared temp guage to read the temp of coolant going into heater core vs. temp coming out of it. This should be very close reading (within 5-10 degrees) If you have hot coolant going in and coming out then the assumption is that the blend door had malfunctioned in heater box and needs to be serviced. Sorry, but I don't have any tips to replace actuator on this as they change location of actuator on every model.

 

If truck has A/C check for a blocked climate control filter