When set to HEAT mode, the system will shut down once the room reaches the set point. The fan will cycle on every few minutes to sample the air temperature. This is normal operation.
Other causes:
- The ductless (split air) unit could be too large for your room and is "short cycling." This happens when cold air from an oversized unit bounces off the wall and back towards the unit, creating a room temperature reading that is cooler than the actual temperature.
- This false reading causes the compressor to shut off before the room has truly reached your desired setpoint. While the compressor is off, the "real" room air enters the intake grille, and the thermostat reads that the room is no longer at the set temperature, so it turns the compressor back on.
- The solution is to correctly size the unit's capacity to the room size and demand.