Set Appliance State:

Mains Power Off
Mode selector switch to Off/Reset position
Turn Hot Water Tap On
Hot water temperature control set to MAX
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Mode selector switch to DHW position.
With the aid of a mirror if necessary observe the pump proving spindle.
Does the spindle move quickly and smoothly to fully make the microswitch?