Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
CH Demand
CH temperature control turned to MAX
Disconnect external control wiring from connector 56 on the PCB and make safe
Bypass external controls between connections L and LR using a wire link (see photo below)
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Does the appliance now recognise a CH demand?
A radiator symbol should appear on the display.