1997 ML320 Climate Control

[xyourobob]

My ML320's climate control is not working properly. It appears one of the doors within the vent system is not working properly and unfortunatly it's not allowing the AC to come through. It's an inconsistant problem. Today I put the a/c on and it was working fine until I heard something like a vent door closing in the dash and then hot air was flowing out of the vents. This did not change when I turned off the AC and just tried a cool vent setting. It's always pumping out heat now. Any idea where I should focus my repair effort? Thanks Bob