Set Appliance State:

Mains Power Off
Turn Hot Water Tap On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset appliance if required.
(press reset button once then release).
Does the fan related fault code re-occur?
Note:
It can take up to 1 minute for the house and fan symbol to appear and up to 2 minutes for a fan fault code to be shown.