Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Disconnect red leads from the NTC sensor
Measurement:
Check the resistance across the exposed terminals of the sensor.
The resistance measured will depend upon the boiler temperature, the higher the temperature the lower the resistance.
The resistance should conform to the table below.
The resistance measured will depend upon the boiler temperature, the higher the temperature the lower the resistance.
The resistance should conform to the table below.
| Temperature °C | Resistance in kOhms |
| 10-15 | 19.9-15.7 |
| 15-20 | 15.7-12.5 |
| 20-40 | 12.5-5.3 |
| 40-60 | 5.3-2.5 |
| 60-80 | 2.5-1.3 |
| 80-100 | 1.3-0.7 |
Isolate as per TOPs P4
and refit as necessary