Set Appliance State:
Set Multimeter to Resistance 
CH Demand
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Allow appliance to fire and system to heat until boiler shuts down.
Check temperature of flow pipe close to the overheat stat
Disconnect the leads from the overheat stat
Measure resistance across the exposed terminals of the overheat stat. Expect resistance close circuit zero resistance
OPEN CIRCUIT MEASURED TEMP ABOVE 105°C FURTHER INVESTIGATION REQUIRED
OPEN CIRCUIT MEASURED TEMPERATURE BELOW 105°C
CLOSED CIRCUIT MEASURED
| Isolate Mains Power to appliance as per TOP's P4 |
Check temperature of flow pipe close to the overheat stat
Disconnect the leads from the overheat stat
Measure resistance across the exposed terminals of the overheat stat. Expect resistance close circuit zero resistance
OPEN CIRCUIT MEASURED TEMP ABOVE 105°C FURTHER INVESTIGATION REQUIRED
OPEN CIRCUIT MEASURED TEMPERATURE BELOW 105°C
CLOSED CIRCUIT MEASURED
