Set Appliance State:

Set Multimeter to Resistance Set meter to measure resistance
Isolate Mains Power to appliance as per TOPs P4
Remove connector CN9 from the PCB.

Measurement:

Test 1 :
Measure the resistance between pin 3 (black) and pin 6 (red) on connector CN9.
Expect continuity / zero resistance.
Test 2 :
Measure the resistance between pin 3 (black) and a suitable earth.
Expect a resistance of greater than 1 Mohm.