Your problem sounds like the common blend door problem on the Ford Expeditions, and Ford Explorer. The door is on a vertical axis and when it breaks, it can swing back and forth randomly giving heat or AC or nothing. The difference on acceleration is the force placed on the door swinging it one direction.
You can check the operation by fully opening the glove box, removing the actuator motor on top of the plenum box and examining the blend door axle (the actuator is under the unit on top of the hump behind the flexible black plastic cover. It is on top of the unit, behind the glove box in the 2002 F-350 though). Pictures of the common fail signature are available on the Related Linksbelow. There are several "free" fixes that mostly are worth what you pay for them. The solution on the web site is solid and proven over hundreds of vehicles and will resolve the problem once and for all.
how do i replacement my blend door in my 1998 ford explorer
Do a Google search on Ford Explorer blend door , there are lots of articles and some videos
I do not have heat in the car and the blend door clicks. How do I access the blend door in a 2005 Ford Explorer?
the blend door is stuck open
Do a Google search on Ford Explorer blend door , there are quite a few articles and a couple of videos
If you do a Google search on Ford Explorer blend door there are lots of articles
How do I locate the heater blend door actuator in a Ford f150 pickup
Do a Google search of Ford Explorer blend door , there are lots of articles and some videos
The Mazda truck uses the same heater plenum as the Ford Explorer. Check the Explorer information on www.heatertreater.net for diagnostic and repair information. cgallen
Do a Google search of Ford Explorer blend door , there are lots of articles and some videos
Remove glove box liner. Blend door is located in the heater/evaporator housing. There are several kits available to repair blend door shafts as well as troubleshoot system.
On a 1996 Ford Explorer : The blend door would be INSIDE the plastic case that has the heater core ( and air conditioning evaporator if equipped with A/C ) located below the glove compartment