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 terminals 1 and 2 at connector X4.
Expect a resistance of approximately 152 Ohms.
Test 2:
Measure the resistance between terminals 4 and 5 at connector X4.
Expect a resistance of approximately 152 Ohms.
Test 3:
Measure the resistance between terminal 1 at connector X4 and a suitable earth.
Expect a resistance of 1MOhm or greater.
(O.L is acceptable because this is greater than 1MOhm)
Test 4:
Measure the resistance between terminal 4 at connector X4 and a suitable earth.
Expect a resistance of 1MOhm or greater.
(O.L is acceptable because this is greater than 1MOhm)
Are the resistances measured as expected?