Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
CH Demand
Selector switch to heating
CH 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:

Is the spindle driven out?
Remove CH demand.
Does the spindle retract?