Set Appliance State:
Set Multimeter to Resistance 
Isolate Mains Power to appliance as per TOPs P4
Disconnect Red wires from DHW Sensor Probe
Disconnect Red wires from DHW Sensor Probe
Measurement:
Measure the resistance across the two terminals of the sensor.
Depending upon water temperature the resistance should be approximately as found in the table below:
Reconnect wires after test.
Depending upon water temperature the resistance should be approximately as found in the table below:
| Temperature °C | Resistance in kOhms |
| 30-40 | 8.1-5.7 |
| 40-50 | 5.7-4.2 |
| 50-60 | 4.2-3.0 |
| 60-70 | 3.0-1.7 |
| 70-80 | 1.7-1.2 |
Reconnect wires after test.
Isolate as per TOPs P4
and refit as necessary