Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to DC Volts 
Turn Hot Water Tap On
Gain access to PCB (use Insulation Mat as required)
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Reset appliance if required (Press reset button once then release)
Allow fan to run.
Measure the DC voltage between pin 3 (Black) on connector X20 and the earth point on the boiler chassis.
Expected voltage approximately 5.6 Vdc.
Note:
Each pin on the PCB connector is numbered.
Allow fan to run.
Measure the DC voltage between pin 3 (Black) on connector X20 and the earth point on the boiler chassis.
Expected voltage approximately 5.6 Vdc.
Note:
Each pin on the PCB connector is numbered.
Isolate as per TOPs P4
and refit as necessary