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 and pin 1 on connector A1.
Expect a resistance of 1 Mohm or greater.
Test 2:
Measure the resistance between pin 2 and pin 1 on connector A1.
Expect a resistance of 1 Mohm or greater.
Are the resistances as expected?