An actuator for a valve

An actuator for a valve, with one on the valve housing on tensionable support, which is mounted on carrier thermal expansion element, such as wax cartridge, the output side has an actuator for adjusting a valve pin, one adjacent to the expansion element electric heating element and a control circuit for controlling the heating in dependence on an opening position of the valve determining control voltage, characterized in that a position measuring device (11) is provided which detects the position of the actuator (5) and outputs a position signal in dependence on the position of the actuator (5) or of a variable from it the component, and that the control circuit (20) controls the heating in dependence of control signal and position signal.