Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Remove red leads to flow thermistor
Measurement:
Measure for resistance across the exposed pins of the flow thermistor.
The resistance will vary according to the boiler temperature but should conform approximately to the table below:
The resistance will vary according to the boiler temperature but should conform approximately to the table below:

Isolate as per TOPs P4
and refit as necessary