Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove the plug JP11 from the control box
Measurement:
Measure resistance across the white wires at the plug (7 & 8).
HARNESS & DHW SENSOR RESISTANCE
Resistances vary with temperature and should conform approximately to the table below:
| Temperature Range (°C) | Resistance Range |
|---|---|
| 0°C to 10°C | 19.0kΩ - 30.0kΩ |
| 10°C to 20°C | 12.0kΩ - 19.0kΩ |
| 20°C to 30°C | 8.2kΩ - 12.0kΩ |
| 30°C to 40°C | 5.6kΩ - 8.2kΩ |
| 40°C to 50°C | 3.9kΩ - 5.6kΩ |
| 50°C to 60°C | 2.8kΩ - 3.9kΩ |
| 60°C to 70°C | 2.0kΩ - 2.8kΩ |
| 70°C to 80°C | 1.5kΩ - 2.0kΩ |
| 80°C to 90°C | 1.2kΩ - 1.5kΩ |
| 90°C to 100°C | 900Ω - 1.2kΩ |
Note: Clicking on the resistance table will switch between table and graph view.
Isolate as per TOPs P4
and refit as necessary