Set Appliance State:

Set Multimeter to Resistance Set meter to measure resistance
Isolate Mains Power to appliance as per TOPs P4
Remove connector CN4 from PCB

Measurement:

Test 1:
Measure the resistance between pin 3 (Black) and pin 6 (grey) on connector CN4.
Expect a resistance of 3.4 ohms approximately.
Test 2 :
Measure the resistance between pin 3 (black) on connector CN4 and a suitable earth.
Expect a resistance of greater the 1Mohm.