Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Slide the connection PCB out
Remove X3 (timer) connector from the connection PCB
Note.
Ensure the connection PCB is positioned safely
Ensure NO demands
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Does the Central Heating demand (radiator symbol)
still flash with X3 connector removed ?