Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove the 20 way connector from the PCB

Measurement:

Test 1: Measure the resistance between the two black wires
terminal 3 and 4 counting from left to right.
Expect approximately 165 ohms
Test 2: Measure the resistance between the two black wires
terminals 5 and 6 counting from left to right.
Expect approximately 165 ohms
Test3: Measure the resistance between each of the black
wires 3,4,5 and 6 to earth.
Expect open circuit on each test
Note:
The colours of the wires may vary but the terminal locations will remain the same.