The system contains a voltage reference input positioned to be compared to an initial generator output voltage of an engine generator control unit by a subtractor circuit. A resistive voltage divider has at least one input series resistor, a subtractor input, at least two secondary resistors, and a ground. The input series resistor is disposed between the voltage reference input and the subtractor input. The secondary resistors are disposed between the subtractor input and the ground. At least two transistor switches connected between the secondary resistors and the ground. The reduced generator output voltages are from the input series resistor and the secondary resistors.