Set Appliance State:

Mains Power Off
DHW Demand
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Observation:

Allow the fan to run and observe the 3 L.E.D's on the front left hand side of the facia.
As the fan runs does the fan fault code display?
Note:
Fan fault code is identified by the left hand L.E.D flashing with the middle and right hand L.E.D being lit permanently.