Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Remove the diverter valve actuator from the diverter valve body and rest in a safe place where it can be observed
Note:
The diverter valve motor can be removed without draining the appliance. Pull the motor assembly towards you. The assembly will slide free from the valve. It could be necessary to depress the lever in the diverter valve body by approx. 5mm to align the motor and body on reassembly
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Watch the diverter valve actuator movement.
1) The actuator should move slowly to its lowest position and then back up to its mid position. If the actuator only moves up (i.e. was in the lowest position) then repeat the test by turning the mains power off & on and watch the actuator move again when it should behave as above.
2) Turn On CH demand.
The actuator should now move to its lowest position.