Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Disconnect plug marked X20 from the PCB
Measurement:
Test 1:
Measure the resistance across the terminals 9 (blue) and 18 (red) at the disconnected plug X20.
Expect a resistance of approximately 55 Ohms.
Test 2:
Measure the resistance between terminal 18 (red) and a suitable earth.
Expect a resistance of 1Mohm or greater.
(O.L is acceptable because it is greater than 1Mohm)
Measure the resistance across the terminals 9 (blue) and 18 (red) at the disconnected plug X20.
Expect a resistance of approximately 55 Ohms.
Test 2:
Measure the resistance between terminal 18 (red) and a suitable earth.
Expect a resistance of 1Mohm or greater.
(O.L is acceptable because it is greater than 1Mohm)
Isolate as per TOPs P4
and refit as necessary