Lennox split AC, whole house two zones. Found system frozen at arrival. Reason. Was because the upstairs damper had malfunctioned and was stuck close even though it was calling to run. I thawed the system and replaced the damper. Tested, and ac is now working very well. Also opened the manual dampers in the attic for each room. Another contractor at some point had came and closed 2/3 of all the supply Air upstairs.
