Set Appliance State:
Set Multimeter to Resistance 
Isolate Mains Power to appliance as per TOPs P4
Disconnect the hot water thermistor at its inline connector
Disconnect the hot water thermistor at its inline connector
Measurement:
Measure the resistance across terminals of the inline connector that runs to the thermistor in the thermal store. Resistance will vary according to the temperature of the water. The lower the temperature the higher the resistance.
The resistance should conform to the table below:
Reconnect inline connector after test.
The resistance should conform to the table below:
| Temperature °C | Resistance in kOhms |
| 30-50 | 9.8-4.7 |
| 50-70 | 4.7-2.4 |
| 70-90 | 2.4-1.3 |
| 90-110 | 1.3-0.1 |
Isolate as per TOPs P4
and refit as necessary