The ICM325A low ambient head pressure control ensures the condenser fan runs at an optimal speed for maximum efficiency. If the system pressure gets too low or the condenser temperature gets too cold, the ICM325A lowers the fan speed accordingly. Other head pressure controls on the market just turn the fan off completely. This method results in inconsistent head pressure, inconsistent cooling, rattling pipes & ducts, system leaks, and ultimately a shortened life span of the condenser fan motor and compressor.