A solid state control circuit controls handlebar heaters on a snowmobile or similar responding loads. Circuit is supplied by AC voltage with variations in frequency and waveform of the AC input. A portion of this input is rectified and compared with a rectified portion of the output voltage. The difference between these two signals is used to supply two amplifying devices. A control signal to a switching device selectively connects one polarity of the AC to the load. The circuit is adapted to be disabled by the application of an external voltage typically from a brake light switch and bulb. The opposite polarity of the waveform is controlled from the AC to the load by sensing the DC component across the load and using a second switching device to drive this DC value to a negligible value. Components are incorporated that are sensitive to temperature and also waveform to produce higher output heating at high vehicle speed and lower operating ambient temperatures or airflows.