Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
CH Demand
Turn Hot Water Tap On
ON/OFF Switch ON
Summer/Winter button set to Winter
CH Temperature selector to maximum
DHW Temperature selector to maximum
Remove the diverter valve head
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Diverter valve motor spindle should be fully out (DHW position).
Turn DHW tap off.
Does spindle retract to the CH position?
There may be a delay before demand is recognised.