Set Appliance State:

Set Multimeter to Resistance Set meter to measure resistance
Isolate Mains Power to appliance as per TOPs P4
Gain access to PCB
Disconnect M3 from the PCB

Measurement:

Measure the resistance between pin 5 (black)
at M3 on the PCB to a suitable earth point.
Resistance should be at least 1M Ohm.