Dodge Durango Rear A/C & Heat Blow Outside Air Temperature

This past winter I noticed the air coming out of the rear vents on our 2002 Durango was cold even though the controls were set to hot.

This spring I noticed that the air coming out of the rear vents was luke warm even though the controls were set to cold.

I tried using the rear controls as well as the front controls that control the rear temp, but there was no difference.

Both the A/C and Heat in the front work fine. The heat is hot and the cold is cold, but the air temperature in the rear feels like it's the same temperature as it is outside.

Any suggestions on how to diagnose the problem?

Thanks