Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector X3 from the PCB

Measurement:

Test 1.
Measure for resistance across pins 6 (brown) and 7 (blue) of connector X3.
Expected resistance greater than 1 MOhm (or O.L).
Test 2.
Measure for resistance across pin 6 (brown) of connector X3 and a suitable earth connection.
Expected resistance greater than 1 MOhm (or O.L).
Note:
Pins may be multicoloured.