I've read all the info and watched the videos.

How do I determine if my problem is the door?
With my heater on floor/panel and the fan on low you can feel the slightest warmth out of the vent. Turn the fan up and it gets cold. I can get in the floorboard and hear the motor when I adjust the temp control but I do not hear the door or any other noises. Just trying to figure out where to start. Thanks

By the way - it's been 10 yrs since I owned a ford. After 1 dodge and 2 Chevy's with a POS Nissan - I'm glad to be back.

 

Sounds like a bad thermostat or a clogged heater core to me.

 

I had a 2003 Screw and here's my tale of heater core woe...


I had a vacuum draw due to a leaky head gasket. Coolant got out, air got in to replace it. It would pull air into my coolant system, and the highest point of the system is the hoses leading to the heater core. So once an air bubble builds up, it acts like a plumbing P-trap and doesn't allow any fluid to get to the core. If I had the heat blasting, and it was warm, that meant I had enough coolant and it was getting up there. But as soon as the level dropped a bit, and I accelerated or decelerated enough to slosh the coolant back out of the core, it went cold. Then I'd have to replenish coolant. Last winter was the final straw, so I got my 2015 now. But man oh man.... Michigan winters are impossible to ignore.

So take your truck up to a shop that can do a coolant system pressure test. They'll be able to tell if it is an exhaust-path coolant leak, or a head-gasket-path coolant leak. It would have been a $2000 job to rip the engine out to replace the gasket, or $1600 for a replacement engine. The guy honestly didn't want me to bother yanking an engine from a 200K mile, 12 year old truck with lots of beat up abuse and hard miles. He said take that repair money and use it on the down payment. Which I did.

 

I sure hope I don't have that problem. Hoses all get hot and the radiator is full. Taking it to the shop next week.
One thing I thought was weird - when I opened the radiator it made a woosh noise. Kinda like opening a soda.

 

Of course it will - it's under 15 psi of pressure if it's warmed up.

However, you may have an air lock. Leave the cap off and let it idle for 20 minutes, then check the level.

 

Yes, yes, to Obi-Wan you listen!

 

Heater core was clogged. Heater works better but still not great. I think I need to flush it out again.