Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Disconnect plug ST1 from the PCB
Measurement:
Test 1:
Measure the resistance between the yellow and brown wires on the disconnected plug.
Resistance should be approximately 44 Ohms.
Test 2:
Measure the resistance between the either wire on the disconnected plug to a suitable earth point.
Resistance should be greater than 1M Ohm.
Measure the resistance between the yellow and brown wires on the disconnected plug.
Resistance should be approximately 44 Ohms.
Test 2:
Measure the resistance between the either wire on the disconnected plug to a suitable earth point.
Resistance should be greater than 1M Ohm.
Isolate as per TOPs P4
and refit as necessary