What do you do if the heat is not working on a Ford F-150?

Answer 1

Get the engine up to full temperature. Make sure the thermostat is working properly. If it is not providing hot water, replace the thermostat. If the thermostat is working properly, put your hand on both hoses going into and out of the heater core. Both should be hot. If only one is hot, the core is probably plugged and not passing the hot water though. If this is the case, the heater will not function properly. The heater core either needs to be back flushed until a good, steady stream of water passes through it or it needs to be replaced. If the heater core is working properly ( both heater hoses are hot), you may need to check the air blender door located under the dash behind the glove compartment. Take out the glove compartment box and see the cable that moves when you turn your heater control from hot to cold. The air blender box door may not be moving as far as it should to get just hot air. If that is the case, look where the heater control cable runs through a white part with a tab on top of it. Pull the white tab forward and move the red cartridge inside of it to the right one or two notches and release the white tab to lock it into place. Now try the heater cable by moving it to full heat and see if that improves the situation. It should provide hotter air from the heater.