Our Halcyon Inverter heat pump seems very temperamental. It seems to randomly shut itself off. Even if I set the temperature to 88 degrees, it will stop pumping in heat when the room temperature is 64. Sometimes it works really great. We have two reticules or whatever they are called. And sometimes turning down one, will shut off the one in the other room. Very inconsistent.

That has a speed controlled compressor and it is DC not AC. If you call for service be sure to make sure they know EXACTLY whet they are doing. 99.9 percent of the companys out there will not. Service is to complex of a issue to discuss here and the cause could be many different things.