Set Appliance State:
Set Multimeter to Resistance 
Isolate Mains Power to appliance as per TOPs P4
Disconnect Red Wires from connections 7 & 8 on the connector block
(Ensure other end wires disconnected from the connector block are
connected to the hot water sensor)
Ensure DHW is cool
Disconnect Red Wires from connections 7 & 8 on the connector block
(Ensure other end wires disconnected from the connector block are
connected to the hot water sensor)
Ensure DHW is cool
Measurement:
Measure the resistance across the disconnected wires.
Note: Resistance measured will vary according to the boiler temperature, the cooler the boiler the higher the resistance. The resistance should conform to the table below.
Reconnect wires after test.
Note: Sensor is adjacent to the diverter valve.
Note: Resistance measured will vary according to the boiler temperature, the cooler the boiler the higher the resistance. The resistance should conform to the table below.
| Temperature °C | Resistance in kOhms |
| 10-20 | 19.9-12.4 |
| 20-30 | 12.4-7.9 |
| 30-40 | 7.9-5.2 |
| 40-50 | 5.2-3.5 |
| 50-60 | 3.5-2.4 |
| 60-70 | 2.4-1.7 |
| 70-80 | 1.7-1.2 |
Note: Sensor is adjacent to the diverter valve.
Isolate as per TOPs P4
and refit as necessary