Set Appliance State:
Set Multimeter to Resistance 
Isolate Mains Power to appliance as per TOPs P4
Measurement:
Remove the green wires from the DHW sensor and measure the resistance across the terminals on the sensor.
The resistance measured will depend on boiler temperature.
The resistance measured will depend on boiler temperature.
| Temperature °C | Resistance in kOhms |
| 10-20 | 10.0-6.0 |
| 30-40 | 3.0-2.5 |
| 50-60 | 1.8-1.6 |
| 70-80 | 1.0-0.5 |
Isolate as per TOPs P4
and refit as necessary