Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove connector from the fan and X3 connector from PCB
Measurement:
Measure the resistance of each wire of the harness.
Test 1. Pin 6 (Brown X3) to pin 3 (Brown wire, fan connector).
Test 2. Pin 7 (Blue X3) to pin 2 (Blue wire, fan connector).
Test 3. Pin 1 (Green/Yellow, fan connector) to Boiler chassis.
Expected resistance, continuity (zero resistance) on each test.
Test 1. Pin 6 (Brown X3) to pin 3 (Brown wire, fan connector).
Test 2. Pin 7 (Blue X3) to pin 2 (Blue wire, fan connector).
Test 3. Pin 1 (Green/Yellow, fan connector) to Boiler chassis.
Expected resistance, continuity (zero resistance) on each test.
Isolate as per TOPs P4
and refit as necessary