Boiler does not start at all, no display or lights, as if completely dead.

How to Fix / Troubleshooting

Safety first: Ensure your hands are dry and the area is safe before touching electrical components.

User checks:

Verify that other electrical appliances on the same circuit are working.
Check the consumer unit for a tripped breaker or blown fuse and reset/replace if appropriate.
Confirm that any external boiler switch or fused spur is turned on and the fuse is intact.

Technician checks:

Test for mains voltage at the boiler's mains terminal block.
Check and replace the internal fuse on the PCB if blown, and investigate the cause.
Inspect the main PCB for damage to the power supply section and replace if necessary.

Do not bypass fuses or operate the boiler with suspected electrical faults.