2001 Expedition Front A/C blows hot

I have recently purchased a 2001 Expediton XLT, it has 48K on it. The A/C was running fine this a.m. but now it only blows hot air all of the time. No recent work has been done on it. There are not errors lights or anything showing on dash and no blown fuses. No matter what position I put the controls on the tempature stays the same very hot. Also changing to panel, defrost also makes no change on the tempature but, it does blow out the correct guides. The rear Heating / AC unit runs fine and can switch from cold to hot.

Any information would be greatly appreciated.

Thanks for your help.

Mark

I have a 1999 Expedition Eddie Bauer 4x4 and the crazy thing has started doing the same thing.
I have had it since April this year and it used to run cold... then I took it in to Wal Mart and had the automotive guys change the oil and filter & the air filter & check my junk for me... they put a stinkin' FRAM oil filter on it (hate those things) and every since they did it, the front air takes to fits of not blowing cold. The rear air is as usual, but front air blows warm, and sometimes even heat.
Anyone know why ? The guys at wal mart said they didn't do anything that could have caused it, but it didn't happen till they stuck their fingers in my truck.

blend door motor or temp switch......have fun if blend door motor.
to check motor, look under pass. side dash for a little white or black box that bolts to the heater box,there is a rod that goes into hte heater box, change the temp switch position and that rod should turn,that controls your blend door.