Ok I need help again. Starting yesterday my AC display started showing EXT ( whatever the current outside temp is ) on the digital display. I try to manually dial the temp down to 60 and turn the fan to low which is where I usually like to run the system and it will go back to the EXT display after a few seconds and I'm no longer able to get cold air from the vents. It's like the system is telling me that because it's colder outside now that it doesn't need to run the AC but I want to run it instead of getting the air from outside.

Any ideas on what might be causing this would be greatly appreciated.