The Rinnai M6J-1-3 Water Heater By-Pass Servo Assembly 403V regulates water flow through the designated bypass circuit in a compatible water heater. This assembly uses an electrically operated servo mechanism to adjust the bypass valve according to commands from the heater’s control system. Its operation supports proper water flow management and contributes to the unit’s intended temperature regulation process. A correctly functioning assembly supports consistent water heater performance and coordinated operation with other internal components. Replacing a faulty or worn servo assembly can restore bypass control and address related operating issues. This replacement component is designed for compatible Rinnai water heater models.