Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector X18 from the PCB

Measurement:

Test 1:
Measure the resistance between the Blue and Black wires at X18.
Expect approximately 121 ohms.
Test 2:
Measure the resistance between the Brown and White wires at X18.
Expect approximately 57 ohms.
Test 3:
Measure the resistance between the Brown, Blue, Black and White wires to Earth.
Expect open circuit on each test.