I have a 2003 Expedition that will blow cool air in the front seats but the vents in the back blow warm air. How can this be and how can I fix it?

 

The usual cause for that on an Expedition is a failed blend door actuator on the rear MVAC case.

It can also be cause by a slightly low system charge, but there is no way to tell without reading both the High and Low side system pressures.

My bet is the actuator

 

Thank You Isrx for your reply. I have been researching the rear HVAC that you mentioned. I found a few threads that talk about a "thunping" in the right rear when the AC is turned on and how to fix it. My problem started with that thumping and my husband found a gear with broken teeth. He replaced it, reassembled the car, and the thumping is gone but like I said the air still doesn't blow cold. He is not very willing to help me further with this so I am trying to learn this on the fly and see what I can do about it. I am not afraid of tools just want to have a good idea of what I need to do before I get started. Is my current problem related to that gear? Can you guide me to the actuator you spoke of? Thank you so much for your patience with my questions.

 

The actuator is about the size of a cell phone, usually black in color. Is that what he replaced? Here's one:
http://autoparts.pricegrabber.com/en...m97482661.html

There is a gear inside of the actuator that breaks, but it would have to be disassembled to see it. The gear is not replaced separately.

 

I had mine replaced two times in my 03 Expy....it does make the thumping noise in the right rear quarter panel, as mentioned