Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Disconnect sensor plug from the PCB (CN14)
Measurement:
Measure resistance across the two white wires on
the right side of plug CN14.
The resistance measured will depend on the boiler temperature but should conform to the table below.
the right side of plug CN14.
The resistance measured will depend on the boiler temperature but should conform to the table below.
| Temp °C | Resistance in kOhms | 20 - 30 | 8 to 16 |
| 30 - 40 | 6 to 10 |
| 40 - 50 | 3.9 to 8 |
| 50 - 60 | 2.5 to 5.5 |
| 60 - 70 | 1.5 to 3.0 |
Isolate as per TOPs P4
and refit as necessary