Liquid sensor

A liquid sensor comprising a frame, a temperature sensitive expansion element mounted on the frame, an electrical heater element operatively associated with the expansion element for applying heat to the expansion element to raise its temperature above ambient, and means actuated in response to changes in length of the expansion element for indicating change in temperature of the expansion element, the liquid being sensed being brought into heat transfer relation with the expansion element for removing heat from the expansion element to lower its temperature and actuate said indicating means, the expansion element including an elongated strip anchored at both ends to the frame, an elongated flat spring member forming a switching element anchored at one end to the frame, the other end of the spring member moving with bending of the spring member about the anchored end, and means connecting the spring member to the expansion element so that the spring member is deflected by lateral movement of the expansion element between the anchored ends.