I have two exact Cartier Infinity AC units cooling my house, one takes care of the E side, the other W. Few months ago the W unit stoped working at times with Static Pressure TOO HIGH (6.58 inches) showing on the thermostat display. I also noticed that the air flow coming out of the registers was barely noticeable. I installed new original filters on both units, but same problem. I called the AC guy and he told me the duct needs to be replaced. I asked him to check for air flow restrictions. He took the air handler apart and found that the blower runs at high (1750 CFM) while autotest runs) but there is no air suction at the input, and of course no air at all going out, with the filter removed and the exit going into the duct removed.
I do not doubt that the duct in the atick may not be the best design, but my question was "how this AC has been working like this since 2008, AND the other exact system on the E side of the house works well. In my opinion, as an electro-mechanic enginer, there is somthing else wrong with my W AC unit. If any of you are familiar with this system plese help!
I assume it's not just the AC coil freezing restricting the airflow. I'm sure the tech would have noticed that. Likely you have insulated flex duct in the attic and maybe an animal made a nest and it's full of insulation. You could go up there with some tin tape and side cutters and cut the flex, remove the restriction, and tape the flex back together. If an animal has been living in it you may want to replace it.