Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector X4 from the PCB

Measurement:

Test 1.
Measure the resistance between pin 8 (grey) and
pin 17 ( grey) on connector X4.
Expected resistance approximately 116 ohms.
Test 2.
Measure the resistance between either pin 8 (grey) or pin 17 (grey) to a suitable earth point.
Expected resistance greater than 1 MOhm.