Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove connector X25 from the PCB
Remove the connector from the Stepper Motor
Remove the connector from the Stepper Motor
Measurement:
Measure the resistance across each of the wires in the harness to the stepper motor as below.
Expect continuity on each wire in the harness.
Also inspect the condition of the harness visually to check there are no sections of damaged insulation.
Note: Each pin on the PCB connector is numbered.
| Pin on connector (X25) | Stepper Motor Connector | 5 (Blue) | Blue |
| 3 (2 Reds) | Each Red |
| 11 (Black) | Black |
| 10 (Green) | Green |
| 4 (Brown) | Brown |
Expect continuity on each wire in the harness.
Also inspect the condition of the harness visually to check there are no sections of damaged insulation.
Note: Each pin on the PCB connector is numbered.
 gas setup and fan.gif)
 pcb in situ.gif)
 connector x25.gif)
 stm connector.gif)
Isolate as per TOPs P4
and refit as necessary