[rohrmann]

Several years ago, our front A/C stopped working, and I tried everything to solve the problem. I finally removed the cover of the control box above the filter. I discovered the circuit board was corroded, including the connections where the phone cable plugs in to it. I ordered a new box, about $100 at the time, and that fixed the problem. Then, a year or two after that, the CCC2 thermostat showed a garbled display and would not clear, so I ordered a new one, and that has worked fine ever since. The phone cable goes from the thermostat to the main A/C (zone 1), ours is the 15K unit, and from there goes to the bedroom unit, the 13.5K unit (zone 2), so if the cable or something in the control box fails, on the part of the system beyond the first control box, your zone 1 unit will function fine, and the zone 2 unit will have issues. Be sure to check the circuit board in the control box of the problem unit, remembering to turn off the breaker to that A/C as it will be energized if you don't.