Abstract: A thermostatic switch with a pair of switch contacts opened and closed by a first pivotably mounted lever urged in one direction by a spring and in the other by a bellows to alternately open and close the switch to operate a compressor. A manual switch can be rotated to vary the spring force through a cam follower and is also movable in and out of the housing. When moved into the housing a second lever is pivoted to engage the first lever and the cam follower so the force required by the bellows to pivot the first lever is such that defrosting occurs.