Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector CN4 from the PCB
Ensure that the cold mains supply is ON
(Turn the lever 90° anti clockwise until it is facing down)

Measurement:

Measure the resistance between pin 16 (green)
and pin 17 (green) on connector CN4.
Expected resistance open circuit.
Run a hot tap at 2 litres/min and repeat above test.
Expected resistance short circuit.