Just bought a 1998 Expedition and it has the famous constant clicking while the heat is on. I know it is either the blend door or actuator but would like some input. Heat will blow out defrost or panel depending on what i select from the "****." Since the air will flow from panel, floor or defrost makes me think it is the actuator. Anyone with more wisdom than I have any thoughts about my problem? I have searched the forum and found the blend door fix--heatertreater so I know what has to be done if it is the blend door... Thanks in advance...

 

Usually in the front it is the axle of the blend door itself. In the back it is the gears in the actuator.

 

Looks like you need to remove the dash, and replace the blend door, as it's more than likely going to be the "axle" on the blend door itself, that is going bad. I know there is an easier way to fix the "blend door" (by looking on eBay or even here) but I would just do it the correct way, and while you are in there, replace the "heater core" as well. I have seen a few cases, where as soon as the "blend door" was fixed (the easier way), the heater core went bad. It's really not a bad job to do. Book I believe calls for 7 or 8 hours, but if you are mechanically inclined, it really should only take about 3 to 4 hours.

Good Luck with it.