The Better Pack heater can be opened by lifting the label on both ends and removing the hidden screws. You will also need to remove the adjustment knob. If you find a lot of corrosion you may need to replace the assembly. If you are able to remove the plate, transfer the thermostat to your new plate. You will need an electrical connector (not included) to splice the wires together. A packet of white paste is included and is applied on the underside of the heater to help with heat transfer and to minimize corrosion.
