Set Appliance State:

CH & DHW temperature controls set to MAX
Ensure boiler is cool
Run hot water tap with a flow rate of 3 l/min
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset the boiler / cancel pump purge as necessary.
Does the fan run?
If a fault code now shows click here.