Came out to call. Customer said both his units had froze up since the start of this week. He turned the upstairs system off to let it thaw but still ran the downstairs. The downstairs unit was frozen over. Both the upstairs and downstairs filters were dirty. Customer will replace them. With customers permission, I ran the heater on downstairs unit to thaw it out while I checked upstairs unit. I cycled upstairs unit on and found it low on charge. The upstairs equipment is original to the home (1996), and there is a leak in the system. I discussed with customer about refrigerant needed and other options, like replacement of system. Customer wanted to just add the refrigerant for now and look into replacing the system later this year. I added 1.6lbs of R-22 to unit to get correct superheat. After I checked the upstairs system, I cycled downstairs unit on and checked charge. System was slightly off on charge. Customer had me add 1lb to downstairs system. Both AC’s are cooling properly at