Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Disconnect the wires from the flue sensor and thermal fuse
Disconnect connector X5 from the PCB
Disconnect connector X5 from the PCB
Measurement:
Check for (continuity) zero resistance of the wires for the flue sensor and thermal fuse to the PCB (pins 2 and 3 of X5).
Inspect the harness for good overall condition.
Note:
As the thermal fuse and flue sensor are wired in series, three resistance checks will be required to confirm harness:
PCB to Flue Sensor;
Flue Sensor to Thermal Fuse;
Thermal Fuse to PCB.
Inspect the harness for good overall condition.
Note:
As the thermal fuse and flue sensor are wired in series, three resistance checks will be required to confirm harness:
PCB to Flue Sensor;
Flue Sensor to Thermal Fuse;
Thermal Fuse to PCB.
Isolate as per TOPs P4
and refit as necessary