Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector CN1 from the PCB

Measurement:

Test 1. Measure the resistance between pins 3 and 4 on connector CN1.
Expected resistance greater than 1Mohm.
Test 2. Measure the resistance between pin 4 and a suitable earth connection.
Expected resistance greater than 1Mohm.
(O.L is acceptable because it is greater than 1MOhm)
Are the resistances measured as expected?