Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove the secondary sensor from the secondary heat exchanger
Measurement:
Measure resistance across the sensor.
PLATE HEAT EXCHANGER SENSOR
Resistances vary with temperature and should conform approximately to the table below:
| Temperature Range (°C) | Resistance Range |
|---|---|
| 0°C to 10°C | 20.0kΩ - 34.0kΩ |
| 10°C to 20°C | 13.0kΩ - 20.0kΩ |
| 20°C to 30°C | 8.0kΩ - 13.0kΩ |
| 30°C to 40°C | 5.3kΩ - 8.0kΩ |
| 40°C to 50°C | 3.5kΩ - 5.3kΩ |
| 50°C to 60°C | 2.4kΩ - 3.5kΩ |
| 60°C to 70°C | 1.7kΩ - 2.4kΩ |
| 70°C to 80°C | 1.2kΩ - 1.7kΩ |
| 80°C to 90°C | 900Ω - 1.2kΩ |
| 90°C to 100°C | 700Ω - 900Ω |
Note: Clicking on the resistance table will switch between table and graph view.
Isolate as per TOPs P4
and refit as necessary