Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Remove diverter valve motor
Do not hold the actuator for this test
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Observation:

Run DHW Tap.
Is the diverter valve motor spindle in the DHW position i.e. fully extended?