A circuit and method for controlling a voltage applied to a coil to actuate electromechanical relays or contactors. The strength of a magnetic field operating the coil is a function of the product of the number of turns of the coil wire and the magnitude of current, in amperes, passing through the coil wire. An adjustable voltage regulator provides a regulated voltage as an output to a first terminal of a coil to energize the coil based on the temperature of the coil as sensed by a temperature sensing device located proximate the coil. The regulated voltage is controlled based on the sensed coil temperature to consistently provide a current of optimal magnitude to actuate the coil at the sensed temperature. A transient voltage suppression circuit may be used with the coil to suppress back electromotive force generated currents and voltages when the coil is de-energized.