Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector A1 from the PCB

Measurement:

Test 1:
Measure the resistance between pin 4 on connector A1 and a suitable earth.
Expect a resistance of 1 MOhm or greater.
Test 2:
Measure the resistance between pin 2 on connector A1 and a suitable earth.
Expect a resistance of 1 MOhm or greater.
Are the resistances as expected?
Note:
The position and orientation of connector A1 may vary but the test remains the same.