2002 S60 2.4T AC Vent Closing Issues with ECC

[TammyC]

My ac is functioning properly when the outside temperature is less than 80 degrees. There is good air flow from the vents and I am able to switch from manual to auto and feel cold air. When the outdoor air is above 80 degrees, the ac is on full blast when AUTO is selected. It works for about 20 seconds and then switches itself to a low vent flow. The temperature remains cool, but there is definitely decreased air flow. You can feel a a small amount of more air from the defrost area in the front windshield. I recently changed out the evaporator temp sensor thinking that was the problem.

The crazy part is you can hear the air flow decrease. It almost sounds as though it is "sucking in" or something in the vent is closing.

I am going crazy and I am really getting sick of riding with the windows down on 90+ degree days.

Any help with great detail is appreciated. I purchased this car new and have 125,000 miles on it.

[oragex]

In the engine bay, do the A/C lines look frosted? If so, it means the evaporator is freezing thus not letting the air to pass any long. Is the replacement sensor an original Volvo part?