Ac services for 2 2001 Rheem systems Customer recently had home warranty out because up stairs refrigerant line was freezing. Home warranty informed them.it is due to loss of air flow from plugged filters. Down stairs high pressure switch has been bypassed. Filters are over due at this time. Also found that up stairs system is operating low on refrigerant. Power distribution had been replaced recently and tested good for both systems. Water washed condensing coils. Condensing coils have become very brittle and flaking off with water wash. Verified that drainage is flowing freely at this time.