Set Appliance State:

Mains Power Off
On/Off Switch OFF
Set external programmer to call for DHW
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

On/Off Switch On.
Depress DHW mode selector switch while observing the digital clock display.
Does the mode change on the display as the selector button is depressed?
Expected result:
As appliance uses external programmer when mode selector is depressed display should not change.