Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Disconnect connector X7 from the PCB

Measurement:

Test 1:
Measure the resistance between the black and blue wires on X7 connector.
Resistance should be approximately 45 Ohms or greater.
Test 2:
Measure the resistance between the black wire on X7 connector to a suitable earth point.
Resistance should be greater than 1M Ohm.
Test 3:
Measure the resistance between the blue wire on X7 connector to a suitable earth point.
Resistance should be greater than 1M Ohm.