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)
Disconnect connector X11 from the PCB

Measurement:

Test 1:
Measure the resistance across the brown and blue wires at X11 connector.
Expect greater than 1M Ohm.
Test 2:
Measure the resistance between the brown wire on X11 and a suitable earth point.
Expect greater than 1M Ohm.
Test 3:
Measure the resistance between the blue wire on X11 and a suitable earth point.
Expect greater than 1M Ohm.