Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove the 20 way connector from the PCB
Ensure primary heat exchanger is below 60° C
Ensure primary heat exchanger is below 60° C
Measurement:
Measure resistance across the right hand pair of orange wires terminals 19 & 20 counting left to right.
The resistance should conform to the table below:
Refit connector after test.
Note:
The colours of the wires may vary but the terminal locations will remain the same.
The resistance should conform to the table below:
| Temperature °C | Resistance in kOhms | 20-30 | 8.0-16.0 |
| 30-40 | 6.0-10.0 |
| 40-50 | 3.9-8.0 |
| 50-60 | 2.5-5.5 |
| 60-70 | 1.5-3.0 |
Refit connector after test.
Note:
The colours of the wires may vary but the terminal locations will remain the same.
Isolate as per TOPs P4
and refit as necessary