DEFROST When operating in low temperatures the surface of the dehumidifier’s coil/evaporator may accumulate frost/ice and affect the efficiency of the dehumidifier. When this happens the machine will go into periodic defrost mode automatically. This is quite normal. The “Defrost” lamp will come on, the compressor will cease operating and the fan will continue to operate until the frost/ice has thawed. As soon as the frost/ice has melted, the compressor will restart and continue the dehumidifying process.