Connect the leads of the multi-meter across the Line and Neutral prongs of the power plug and perform the following continuity tests:

Main Power Switch Off = should be an open circuit, no continuity. Pressing any switches other than the power switch should have no effect, there should be no continuity (open circuit)

Main Power Switch On = 16 Ohms (approx.) – this is the resistance through the boiler heating coil, and the thermal fuse that protects the boiler from overheating, and the main power switch. If the thermal fuse is blown, or the power switch is bad, the circuit will be open - no continuity.

Main Power Switch On - plus any combination of other switches = 16 Ohms – this only measures the boiler resistance and verifies there are no shorts in the other circuits. It will not reveal any open circuits in the other circuits. The following procedures will test those circuits.