The reversing valve is the specific component that allows a heat pump to switch between cooling and heating modes. It works by changing the direction of the refrigerant flow based on a signal from the thermostat. This is the heart of every heat pump condensers unit we sell. If your system is stuck in one mode, the reversing valve solenoid may need to be checked. This technology allows our one zone wall mount units to provide year-round comfort. It is a marvel of HVAC engineering found in all our Cooper&Hunter and Mitsubishi systems.