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 the resistance between pin 7 (yellow) and pin 19 (yellow) on connector X3.
Test 2.
Measure the resistance between pin 8 (grey) and pin 20 (grey) on connector X3.