Help with heater core... - Diesel Forum

RaiderGrad78 · 10-14-2009, 11:32 AM

I'm about to change out the heater core in my 2000 F250 because I've had no heat for over a year now. How hot is the heater core supposed to get? I let my truck get up to operating temp and both hoses going to the heater core were warm, but not hot. I could hold them indefinitely without it feeling too hot. Next, I took the cover off my heater core and while it was definitely warmer than the hoses, it wasn't so hot that I couldn't put my hand on it and hold it there.

If my heater core is functioning properly, how hot should it get?

joe_400 · 10-14-2009, 11:56 AM

Your heater core should heat up to or very close to operating temps. If your core seems like its getting hot and you still aren't getting heat, check your blend door that switches between hot/cold.

RaiderGrad78 · 10-14-2009, 04:35 PM

Well, I just about ruled out my heater core. I drove the truck around for a while then came back and checked the core...hot as hell. The hoses were very hot as well.

I'm thinking it has to do with the blend door but I cannot find it for the life of me. I found the door to the left of the heater core in the black box that allows air to blow through the air vents. I also found the mechanism behind the heater core box that goes down when you set it to max AC (has the little vacuum hose on the bottom of it). But not the blend door.

I don't have a manual so can someone explain to me exactly where I find it? I have searched and searched but have not found anything that details exactly where the blend door is, to my understanding at least.

RaiderGrad78 · 10-14-2009, 07:06 PM

Well I found the problem and it has to do with the blend door motor. The problem is when I turn the temp dial to hot the motor is having a hard time spinning backwards to open the blend door. When I connect the motor to 12V directly it operates perfectly in both directions by switching the polarity. But, when I connect it back to the connector in the truck and try to operate it normally it messes up again. Since the motor works fine when it's connected to 12V directly this makes me think it may be a temp switch problem?

Also, there is nothing blocking the door as I can move it freely by hand with ease. The motor moves a little bit, but not enough to make a difference in opening or closing the door. It's almost like it's not getting enough power or something.