Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Remove diverter motor from its housing and place in a safe location to observe its movement
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset appliance as necessary.
Observe the diverter motor during the boiler's self-check.
The diverter spindle should slowly move to its fully extended position (if it is not already there).
Turn on HW tap.
The spindle should remain in the fully extended position.
Note:
If you will not be able to observe the diverter movement within 15 seconds of turning the mains power on click here for an alternative test.