Set Appliance State:

Mains Power Off
Ensure No demand for CH or DHW
Set the CH temperature control to 'O' position
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Test 1:
With the CH temperature control in the 'O' position
does the pump still run?
If the pump runs select that option below,
otherwise continue to Test 2.
Test 2:
Turn the control knob to the summer position
(fully anti-clockwise).
Does the pump now run?