PURPOSE: To maintain normal ice producing rate in winter season by controlling an electronic timer by switching a temperature sensor switch to reduce difference between the time while the supplied water is frozen and the time for one period of operation of the electronic timer.

CONSTITUTION: A temperature sensor switch ThSW opens, a compressor c stops, the base current for a transistor Tl is cut off, the reference voltage is determined according to the ratio between resistances R4 and R5 and a condenser C2 for raising the level produces pulses at a long period when the temperature in the freezing chamber dropped to a fixed temperature. If the pulse interval with the ThSW open is 1/2 the pulse interval with the ThSW closed, the speed of an electronic timer IC is reduced to 1/2. Accordingly, the timer period does not become unnecessarily long if the temperature sensor switch is kept opened for a longer time in winter