Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Gain access to PCB (use Insulation Mat as required)

Measurement:

Measure the resistance between pin 8 (red) on X3 at the main PCB to a neutral point (example point shown in picture).
Resistance should be greater than 1M Ohm or open circuit.
Hold the selector switch in the "reset" position.
Resistance should now be short circuit (zero resistance).