Replacing the High Limit Switch

To avoid electrical shock or property damage, move the power switch to OFF and disconnect power.

Remove electrical power supplied to the cabinet.
Remove the control side end panel.
Check the high limit switch by determining the continuity of the high limit. The continuity check can be made at the terminals where the two high limit wires are connected (one wire goes to the thermostat and the other goes to L1 on the quick-connect terminal block). If the unit is cold or the water temperature is below 150°F (66ºC), the high limit should be closed. If the high limit is defective, then replace it by continuing with this procedure.
Remove the cover plate located on the bottom of the cabinet.
Loosen the nuts on the clamp bracket.
Slide the high limit switch from under the bracket.
Remove the electrical wires from the high limit. Replace with a new high limit in reverse order.
Replace the cover plate.
Replace the control end panel.
Turn on the power supply at the breaker box.