Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Disconnect connector X6b from the PCB

Measurement:

Test 1:
Measure the resistance between pin 6 (brown) and
pin 7 (blue) wires on X6b connector.
Resistance should be approximately 4.1kOhms.
Test 2:
Measure the resistance between pin 6 (brown)
on X6b connector to a suitable earth point.
Resistance should be greater than 1M Ohm.
Test 3:
Measure the resistance between pin 7 (blue)
on X6b connector to a suitable earth point.
Resistance should be greater than 1M Ohm.