Remove the cover via the 2 screws located at the BOTTOM of the unit. (2 screws total)

Gently remove the cover by sliding the cover up towards the top and mind the wires and the on/off switch.

The Over Temperature Sensor is located at the top right of the heat exchanger held on by 2 screws and 2 prongs.

Unscrew the 2 screws holding the sensor on and set those screws aside in a safe place.

Using needle nose pliers, remove the 2 connectors from the prongs.

Replace the old sensor with the new sensor, metal side down on the plate.

Using the 2 screws you set aside, screw the sensor in place and reconnect the 2 prongs.

Put the cover of the water heater back on using a screwdriver and the 4 screws you set aside earlier.