2004 Mountaineer rear ceing vents only blow hot air

[bullet bob]

I have a 2004 Mercury Mountaineer. The air conditioner blows cold air fine through the front vents and the vent at the rear of the center console. The blower and temperature for the rear ceiling vents is controlled by a temperature dial and a decade fan switch above the front wndshield. The problem is the vents in the rear ceiling only blow hot air no matter what the temperature setting is. What's causing this and how do I fix it ? Thank you for any help you can give.
Bullet Bob

 

[luvthebeach]

Did you ever find out what was causing this? Thanks.