Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Due to the position of the sensor the test will be carried out at connector X11
It is important to establish that the leads to the sensor are connected and sound
Remove the connector plug X11 from the PCB
It is important to establish that the leads to the sensor are connected and sound
Remove the connector plug X11 from the PCB
Measurement:
Measure the resistance across the red leads at the disconnected connector.
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 |
| 15-20 | 15.6-14.9 |
| 20-30 | 14.9-10.8 |
| 30-40 | 10.8-6.0 |
| 40-50 | 6.0-4.4 |
| 50-60 | 4.4-3.0 |
| 60-70 | 3.0-2.4 |
| 70-80 | 2.4-1.6 |
Isolate as per TOPs P4
and refit as necessary