Where to buy duct work doors

You need to google 2001 f150 blend door actuator replacement. It is slightly right of center above the plastic duct work for the floor area. All lower dashboard plastic is removed to get at it.
Then the ducting is removed.
http://www.autozone.com/repairguides/Ford-Pick-Ups-Expedition-Navigator-1997-2000/Heating-and-Air-Conditioning/Blend-Door-Actuator/_/P-0900c152801e55ed

You need to google 2001 f150 blend door actuator replacement. It is slightly right of center above the plastic duct work for the floor area. All lower dashboard plastic is removed to get at it.
Then the ducting is removed.
http://www.autozone.com/repairguides/Ford-Pick-Ups-Expedition-Navigator-1997-2000/Heating-and-Air-Conditioning/Blend-Door-Actuator/_/P-0900c152801e55ed

See if you can buy or make missing piece to replace broken one...if all else fails duct tape works pretty good.

If you have never done this type of repair, I wouldn't recommend it!
It doesn't cost very much in labor for a trained professional to replace your regulator. You can price the regulator yourself at a local parts store but I would buy the whole assembly! Motor & Regulator together, you should get a lifetime warranty on the parts.

Then let your mechanic install it, I only charge around $60-$70 to install them and the regulator assembly shouldn't be but around $125 or so. Hope this helps. But, below you will find some good info if you intend to replace it yourself. Good luck

Your door panel is held on mostly by plastic clips on the inside of the panel, they go around the sides and bottom of the panel. The easiest way to remove the panel is with a door clip removal tool, you should be able to pick them up at any good auto parts store or tool store.

Also, there is going to be a couple of screws that also holds the panel and works to reinforcement it. They should be around the area where your grab handle is to close the door. Most times you have to also remove the handle assembly to remove the door panel.

You also need to remove the power window/door lock switch panel. Most all the switch panels are held in place with clips as well. A screw driver placed in the right place will pop the switch panel up so you can get access to the wire assembly to disconnect it.

Once you get everything removed mentioned above, your door panel will lift off by pulling up on it. You then will have a plastic sheet/moisture barrier covering the inside panel, remove it without tearing it if possible. If you happen to tear it, you can use duct tape to repair it as well as stick it back to the inside panel.

Your door window regulator will have to be replaced. I recommend buying the regulator and motor as an assembly, it makes it easier and usually you get a lifetime warranty on the parts.

To remove the regulator, locate and remove the bolts that hold the regulator to the panel, you will also have to loosen/remove the bolts holding the door glass to the regulator. I like to use some duct tape to hold the glass in place while you work to remove and replace the regulator.

This job requires the complete removal of the dash from the car and dis-assembly of the duct work to replace the blend door. You must have a factory manual to have any chance of not messing this up completely.

Your ac blend door is broken or the actuator that opens and closes the door is broken. The ac blend door moves up and down to direct air flow through the heater core(for heating) or evaporator core(for cooling).

When the door mechanism breaks, the blend door falls down and you will only have ac but no heating.

You can buy a ac blend door kit for your explorer, they cost about $120 on ebay or other places.
search for Explorer ac blend door kit.

The duct is under the the dash on the drivers side. And you will have to cut open the duct to install the replacement door.

Heres a link to a tutorial of how to do the job.

http://www.heatertreater.net/Ford%20Explorer%2002-08.html

It seems to me if your heater core is hot, and the fan blows cold air, then your ducting is closed off. Try and see if your duct door is opening up. You say you changed out your controls, but it sounds as though it wasn't your controls that were bad, but what they control is not opening up.
It's all well and good that the heater core is getting hot, but if the fan cannot deliver that hot air passing through it, then walah.
It has to be an air duct obstruction. Either the ducting is collapsed, the duct door is not opening, or you have some obstruction blocking the ducting. My guess, because that is all I can give you without seeing for myself, is that the linkeage or solonoid that opens the duct door is not working. Older cars had a cable, but I believe newer use a solonoid to operate the opening and closing of the door. The door is there so you don't get the heat from the core when you are using AC.
Hope this helps.

Refrigerant is not your problem!!!!!!!!

Your recycle door has broken off and fallen over the suction duct to your blower. You can verify this by removing the blower under the dash on the passenger side. Reach up into the duct and if there is a plastic door obstructing the duct, it has broken off. With a little manuvering you can remove the broken door through this hole and you will have air again, just no control of inside or outside air. Dodge has redesigned the housing for this recycle door which is supposed to stop this from happening. The redesigned housing and door come as a unit from Dodge for about $30.00 and this includes the electric actuator. This requires removing the Dash to change the housing so if your not ready for several hours work, take it to a mechanic.

Car manufacturers use the defrost mode as a default for safety reasons. Being they want you to be able to defrost the windshield no matter what. So when something goes wrong the system automatically goes to the defrost mode. You most likely don't have the vacuum hose connected under the dash at the climate control assy. Or if this vehicle doesn't use the vacuum hose style you may have not plugged in one of the connectors under the dash or behind the climate control assy. Good luck.

remove the center console. around the ash tray, the cig-lighter,the radio...the radio just slides out when you stick a small, little slot-head screw-driver in the little slots to release the clips. All the wires unhook and are easy to disconnect and reconnect.. There are screws in the back where the radio was ... remove all the plastic anchor screws and pull out the screws and the anchors...When all the socket screws are removed, take out the control assembly for the HVAC... pullback the entire center console...you will be able to reach up and remove the little plastic enclosed motor assembly that controlls the door...remove the three screws and you have the motor that operates the door...Hind-sight-My cost for the motor assembly was $65.00...I thought that was the solution to the problem...After you remove the assembly, CHECK THE DOOR OPERATION ...I attempted to operate the door and a cracking plastic sound resulted in a completly destroyed duct work area where the motor assembly attached...now I have to replace the door assembly in the duct area, way up there in the dash...I recommend makeing sure that the door operates.. and there is no obstruction causing the door to be stuck,...which caused the damage and breakage of the motor assembly. Before buying the replacement part.