yes
Connect the wiring from the terminal block
to the main PCB securely
no
Is the wiring from the boiler terminal block to the main
PCB connected securely?
yesyes
Connect the cable from the main PCB to
the user interface PCB securely
no
Is the cable from the main PCB to the user interface PCB
connected securely?
yesyes
Replace cable from main PCB to user
interface PCB
no
Does the cable from the main PCB to the user interface
PCB have continuity and is un-damaged?
yesyes
Check for shorts on Pumps/Diverter Valve/
Fan/Spark Generator/Gas Valve and
replace Fuse
no
Is the Fuse on the main PCB OK?
yesyes
Replace main PCB
no
Replace the user interface PCB, still no display?