2003 Ford Explorer won't heat

Check to make sure your plenum is working properly ---in behind your glove department you should see a square box with some wires running through it (box is usually white or clear) turn the heat controls from cold to hot and listen to the box. BTW this box is attached to a big black container that you can probably see from the passenger side floor. If you here a clicking try to remove the box and mess with the controls again. There should be a little extension on this little box and as you turn the heat from cold to hot it moves. The extension looks like a square peg with a rounded side. IF this works well then take a mirror and look down the hole you took this from. This hole is where the penlum sits. It may be cracked -- if this is the case its best to by the repair kit from EBAY cost is about $20 because the dealer will charge you 1500 - 2500 to fix it.