Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove the green plug from the sensor
Measurement:
Measure the resistance across the exposed terminals of the sensor.
The resistance will depend upon the temperature of the boiler the hotter the boiler the lower the resistance. The resistance should conform to the table below:
Temperature °C | Resistance kOhms |
| 20-25 | 11.4-12.5 |
| 25-30 | 9.7-11.4 |
| 30-35 | 7.5-9.7 |
| 35-40 | 6.5-7.5 |
| 40-50 | 5.0-7.2 |
| 50-60 | 3.0-5.0 |
| 60-70 | 2.5-3.0 |
| 70-80 | 1.8-2.5 |
| 80-90 | 1.3-1.8 |
Isolate as per TOPs P4
and refit as necessary