Set Appliance State:
Set Multimeter to Resistance 
Isolate Mains Power to appliance as per TOPs P4
Disconnect red leads from the flow sensor
Disconnect red leads from the flow sensor
Measurement:
Measure resistance across the exposed terminals of the sensor.
Resistance measured will depend upon the temperature of the appliance. The cooler the appliance the higher the resistance and should conform to the table below.
Reconnect leads after test.
Resistance measured will depend upon the temperature of the appliance. The cooler the appliance the higher the resistance and should conform to the table below.
| Temperature °C | Resistance in kOhms |
| 20-30 | 10.0-9.0 |
| 30-40 | 9.0-6.5 |
| 40-50 | 6.5-4.5 |
| 50-60 | 4.5-3.1 |
| 60-70 | 3.1-2.1 |
| 70-80 | 2.1-1.5 |
| 80-90 | 1.5-1.0 |
Isolate as per TOPs P4
and refit as necessary