Performed inspection today on 21 year old units. Upstairs unit has a cracked heat exchanger, a low capacitor, a disconnected plenum, a severely rusted indoor coil, a failed gas valve and a very rough running compressor. The main floor system has a clogged indoor coil with dog hair, a weak capacitor and a refrigerant leak, the system is low on refrigerant. Based on our findings today, it might be time to think about getting a brand new system, supervisor scheduled for Friday morning to replace both systems