skibum7982

Mine is a 1999 F150 with a manual temp/fan contol---it doesn't have that automatic/electronic system.

iowaredneck

I totally forgot to tell you all what happened with my truck. I ended up taking it to the Ford dealership the night before my appt to drop it off. They left it in the garage overnight and the next day the heat worked great. We left it sit outside all day and then tried it again and it worked great. That was two weeks ago and it still works wonderful. I even took it way up north for my deer hunting trip and it never quit. The service guy said he has no idea what happened but everything checked out fine. Miracles never cease and I am thankful to this day.

mwr2452

I'm in the same boat as you. I just changed my t-stat, and gauge still reads where the needle is at the top of the temp icon in the gauge. I've let the truck sit and idle for 20 min last night before going to work and then drove 20 mins to work. It never got hot- in fact, the hottest air came out when it was on LO.
I'm thinking of flushing the heater core next, then I'll look at the flapper door. This sucks!

rawhite71

Hey iowaredneck, just changed the heater core in my 1999 F-150. You have to remove the blender door to do the procedure. As FOMOCO466

rawhite71

Hey, iowaredneck. I just changed the heater core in my 99 F150 4x4 5.4L. As FOMOCO466 stated, you have to remove the entire dash to access the heater core box that contains the heater core and the blender door. Just make sure you disconnect the battery for about an hour before beginning so you don't trip the airbags. If you are a little bit mechanically inclined, you can perform this yourself and save about $1000. However, it will take an entire day, so be prepared.
Good luck!