This terminal block is located in the right side panel of the heater. The purple low voltage wires which route to the processor control board are connected into the top side of the terminals. Due to the very small lead wires on the room temperature sensor, these leads are installed to extend through both setscrews of each position of the terminal block. When servicing or replacing the sensor, care should be taken to ensure that the wires are firmly connected into the terminal block. A poor connection will cause inaccurate room temperature readings at the processor control board.