Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Remove the diverter valve actuator from the diverter valve body

Observation:

Check for free movement of the diverter valve spindle.
It should be possible to push the spindle in with gentle pressure (although the use of an appropriate tool may be required).
When released the spindle should spring back to its original position.
Note:
For clarity the graphic shows the valve removed but it is possible to check the spindle with the valve in situ and the actuator removed.