Set Appliance State:
Gas Off
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to AC Volts 
Remove lower front facia panel
| WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure |
Measurement:
Check for Mains Voltage across terminals marked L (brown wire) and N (blue wire) at connector marked ST12 on the main PCB.
Isolate as per TOPs P4
and refit as necessary