Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Disconnect plug from overheat thermostat
(below heat exchanger, within inner combustion chamber)
(below heat exchanger, within inner combustion chamber)
Measurement:
Measure the resistance between the two spades of the overheat thermostat.
Resistance should be short circuit (zero resistance).
Resistance should be short circuit (zero resistance).
Isolate as per TOPs P4
and refit as necessary