Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to DC Volts 
Remove electrical connector from fan and make safe
| WARNING! - Mains voltage is expected during test follow TOPs P4 live testing procedure |
Measurement:
Reset appliance if required.
Measure for DC volts across pin 17 (purple lead) on connector X20 and
a suitable earth connection.
Expected voltage approximately 22 Vdc.
Note:
Pins are numbered on the connectors.
Measure for DC volts across pin 17 (purple lead) on connector X20 and
a suitable earth connection.
Expected voltage approximately 22 Vdc.
Note:
Pins are numbered on the connectors.
Isolate as per TOPs P4
and refit as necessary