I have a 00 Ford Excursion and only heat blows out of the front vents, the temp control doesn't work at all! The back has it's own controls and will come out cold (not a/c just the outside air) when the front is on (blasting heat). Any idea what this could be?

 

Probably leaked all the freon out. I would check to see if the compressor spins, if it does have the pressure checked.

 

Yep, leak somewheres..... you can get the freon with the dye in it, that works good to find leaks. I have used it many times and with good success

 

I obviously don't know a lot about cars (my husband does all the work) just an observation though.. if all the Freon was out wouldn't it still blow semi-cold (outside) air? The outside air comes out in the back, but nothing but heat in the front.

 

FYI - since this is in the Excursion forum - Don't forget about the Rear A/C lines.
These crack and leak, and my need to be replaced as well.
Had to fix mine last year. O`rielly had both sets (of Motocraft) line replacements for under $600. But if the system has a cracked line and been exposed - it's going to be a bit of a hefty repair bill.

 

The dealer wants $1000+ to replace the rear lines plus diagnosing, freon, etc but OP don't fret yet, I repaired mine with a $20 coupling and did a write up on it in here..............still works fine.

 

If blowing " heat " out the front you may have a blend door issue . If no cool air at rear , you may be low on referigerant . So... sounds like you may have more than one issue . Start with an AC pressure test first ( as stated above ). And go from there . You can be low on referigerant and blow different temps , front to rear , side to side . So start there first . Good Luck !

 

Good idea on the blend door. I had a expedition they had to recalibrate the blend door temp since it was adjustable temp by the push buttons...... they truck never did have good AC..... I had a heater core replaced and the mechanic forgot to recalibrate the blend door, after he did it had great heat and AC.

 

These blend doors are easier to fix, do a search on them in here.

 

If the AC compressor kicks on when in and AC mode, the AC system is not the culprit. In this case the most likely suspect is a vacuume leak usually caused by the ESOF (electronic shift on the fly) hub system that uses the same vacuume line for the front hub engagement as the dash vent box. Look at the hoses(assuming it is 4x4) from the top of the frame rail by the front shocks, to the top of the steering knuckle on the front axle. If theyre cracked, there is your issue.

Problem can also be on the blend door mechanism. Unless, just being simple here, the **** is broken on the inside and dosent turn the spindle. Pull the **** straight out and check it out too.

 

The ac can kick on and off if there is no freon in it.