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Air Condition Unit Lennox 10ACB?

• Have a Lennox 10ACB42-9P AC unit that when turned on it continuously runs. Line ends up freezing as well. Had maintenance man out on 3 occasions, it worked for a few weeks each time and then back to all the time and freezing. I am sure it freezes because it stays on, but what causes it to stay on? I would assume thermostat but it is working fine according to repair guy. Finally got fed up with unit and repair guy so have used window AC's for about 5 years now. Any ideas for troubleshooting. Thank you in advance for assistance.

• Answer:

  Thermostat wires R (hot wire) and Y (cooling) go through your furnace then out to your the contactor relay in the condenser. When you call for cooling your tstat basically jumps these 2 wires together and it sends a 24v signal to the contactor on the condenser and the contacts pull closed letting the main 220v power into the unit and it comes on. So.... (1) These two thermostat wires may be occassionally touching together (probably between the furnace and the condenser), or (2) it may be that your contactor is sometimes sticking closed and not disengaging when the tstat stops sending the 24v cooling signal. If the condenser runs while the inside fan is off, it will freeze up the lines.