The upstairs unit was not blowing cool air and intermittently would not respond to the thermostat at all. I verified the thermostat is bad and replaced the thermostat. I checked on the roof and found the second floor unit had rotted thermostat wires. I replaced the section of wire. The upstairs unit was slightly undercharged, and I charged it back with a pound of Freon. The units operating properly at this time.
