Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Hinge down the PCB housing
Remove 8 way connector from PCB
Remove 8 way connector from PCB
Measurement:
Measure resistance across the two resistors fitted to the low voltage harness.
Resistance depends on boiler kW output but should conform approximately to the table below.
Resistance depends on boiler kW output but should conform approximately to the table below.
| Boiler Output | First Resistor | Second Resistor |
| 12kW | Grey - 150kOhms | White - 6.2kOhms |
| 15kW | Black - 13kOhms | Yellow - 68kOhms |
| 18kW | Grey - 150KOhms | Yellow - 68kOhms |
| 24kW | Clear - 36kOhms | Red - 1.5kOhms |
| 30kW | Black - 13kOhms | Blue - 17kOhms |
Isolate as per TOPs P4
and refit as necessary