Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove ST9 connector from the PCB
If available use the Worcester test PCB to assist resistance test

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
Test 3: 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.