Set Appliance State:
Mains Power Off
Set Multimeter to Resistance 
CH Demand
CH temperature selector to Maximum
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Allow boiler to heat up in CH mode. Remove heating demand.
Disconnect red leads from CH sensor and measure resistance across spade connection on the sensor.
Resistance measured will vary according to the boiler temperature but should conform with the table below.
| Isolate Mains Power to appliance as per TOP's P4 |
Resistance measured will vary according to the boiler temperature but should conform with the table below.
| Temperature °C | Resistance in kOhms |
| 10 | 19.9 |
| 20 | 12.5 |
| 30 | 8.1 |
| 40 | 5.3 |
| 50 | 3.6 |
| 60 | 2.5 | 70 | 1.8 |
| 80 | 1.3 |
Isolate as per TOPs P4
and refit as necessary