Abstract: A control system for a grain harvester. The control system monitors the output of a grain sensor and uses the monitored value to actuate one or more relays having different energization levels. As each relay is actuated it completes a circuit, which is used to modify power that is fed into a control mechanism and which is used to control an operational parameter of the harvester. Depending upon the monitored value of the sensor, the control system will modify the power that supplies a control mechanism that is used to control an operational parameter of the harvester, such as the groundspeed. If the output from the sensor is less that a predetermined threshold, the harvester will operate normally. If the output of the sensor is above a first threshold, the control system will modify the supply voltage. If the output of the sensor is greater than a second threshold, the control system will modify the supply voltage accordingly, and so forth.