2020 Landmark Concord 365 - Erratic AC Operation


2 of 3 units not working correctly. Does not matter the mode (Auto/Hi/Lo). Example - Low Speed selected. Turn on the AC Unit because its hot outside. The fan will come on / compressor will kick on and it may run 5 minutes or 30 minutes. Temperature is not the driving factor because it is Tucson AZ and hot meaning that it is not shutting off because it has reached its requested temp. Basically - I have to turn it off wait a few minutes and then turn it back on and repeat to keep the room cool. Oh and sometimes it will come on low - then turn off and shift to hi speed fan for a short period and then turn back to low or off. Any ideas? Thermostat or Control Board?


Staff member
Your Landmark has a Precision Control Systems (PCS) energy management controller that manages appliances to prevent you from exceeding available power. It should automatically detect when you're plugged into a 50 amp pedestal, which you would need in order to run more than 1 A/C unit at a time.

If you're plugged into 50 amps at the pedestal, it's possible you might be getting only 1 power leg. But if the blowers on all 3 A/C units are working, even if not all together, that would typically mean there's power on both legs.

If there's a poor neutral connection in your main power path, you might have high voltage on 1 leg and low voltage on the other. This can be a very destructive situation as out of range voltage can harm your appliances. If you have a volt meter, try taking some voltage readings at various locations inside and outside, including the outlet for the microwave. You should get around 120V between hot and neutral, and between hot and ground, and close to 0 V between neutral and ground.

There's more information that might be helpful in 2 of our user guides: Landmark 365 and Electrical. They're both in this folder.