all or part of the ram 6 on the same chip with the microprocessor 7 the microprocessor 7 executes the controller operational program although the preferred embodiment shows a microprocessor it is well known in the field that alternative designs could be implemented with discrete logic programmable gate arrays and math chips in place of the microprocessor when the controller is designed to control the heaters for one vehicle the microprocessor 7 is connected directly to an optical coupler 9 if the controller is designed to control heaters for numerous vehicles independently then independent optical couplers and current switches are required for the heaters of each vehicle selection logic 8 is interposed between the microprocessor 7 and the optical couplers 9 as shown in fig1 an advantage of this approach is that all the components for the single heater or the multi heater configuration can be the same except for the select logic 8 the output of each optical coupler acts on the gate of a current switch 10 capable of switching bi directional current with sufficient wattage capacity to power the heaters in most residential and commercial vehicles in an alternative embodiment the optical coupler 9 and the current switch 10 can be located remotely from the controller in the preferred embodiment of this invention the optical coupler 9 provides the means for decoupling the low energy digital processing grounds or electrical returns from the high energy power supply and heater current grounds decoupling is accomplished by the photon transfer link within the optical coupler 9.