Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Disconnect inline connector to the overheat thermostat
(connects grey wire to a black wire, with a clear plastic cover)
Disconnect CN102 from the ignition PCB
(connects grey wire to a black wire, with a clear plastic cover)
Disconnect CN102 from the ignition PCB
Measurement:
Measure the resistance between the grey wire
at connector CN102 to a suitable earth point.
Resistance should be greater than 1MΩ (or O.L).
at connector CN102 to a suitable earth point.
Resistance should be greater than 1MΩ (or O.L).
Isolate as per TOPs P4
and refit as necessary