Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Disconnect wires from the return thermistor
Measurement:
Measure the resistance between the exposed spades on the return thermistor.
RESISTANCE RETURN THERMISTOR
Resistances vary with temperature and should conform approximately to the table below:
| Temperature Range (°C) | Resistance Range |
|---|---|
| 0°C to 10°C | 19.0kΩ - 31.0kΩ |
| 10°C to 20°C | 12.0kΩ - 19.0kΩ |
| 20°C to 30°C | 8.1kΩ - 12.0kΩ |
| 30°C to 40°C | 5.5kΩ - 8.1kΩ |
| 40°C to 50°C | 3.8kΩ - 5.5kΩ |
| 50°C to 60°C | 2.7kΩ - 3.8kΩ |
| 60°C to 70°C | 2.0kΩ - 2.7kΩ |
| 70°C to 80°C | 1.4kΩ - 2.0kΩ |
| 80°C to 90°C | 1.1kΩ - 1.4kΩ |
| 90°C to 100°C | 800Ω - 1.1kΩ |
Note: Clicking on the resistance table will switch between table and graph view.
Isolate as per TOPs P4
and refit as necessary