A thermo-magnetic actuator includes operative components, preferably in a sealed container, from which a rotatable or translatable shaft extends. The shaft is driven by supplying electrical power to a heater in a closed chamber containing a working fluid that expands upon being heated. The expansion of the fluid drives a piston that, in turn, slides a rack coupled to the shaft. A ferromagnetic target is connected to the rack and attracted by a magnetic field produced by an electromagnet that receives electrical power from the same source as the heater. The attraction of the target causes an end of the target to latch magnetically and mechanically and to open an electrical switch, disconnecting current flow to the heater, without disturbing current flow to the electromagnet. The target is released and the rack and target return to their original positions upon termination of current flow to the electromagnet.