Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to DC Volts 
CH Demand
Gain access to PCB (use Insulation Mat as required)
Remove 4 wire connector from fan and make safe
Remove 4 wire connector from fan and make safe
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Measure the DC voltage between pin 17 (red) on connector X20 and a suitable earth.
Expect a reading of approximately 22 Vdc.
Note:
Each pin on the PCB connector is numbered.
Expect a reading of approximately 22 Vdc.
Note:
Each pin on the PCB connector is numbered.
 pcb in situ.gif)
Isolate as per TOPs P4
and refit as necessary