Boiler will not start at all, no lights or display, completely dead

Safety: Electrical work should be done with the supply isolated and by competent persons.

• Check external switch: Ensure the boiler's fused spur or isolator is switched ON.
• Inspect fuse: Turn off the spur, remove the fuse, and check/replace with the correct rating (often 3A). Do not fit a higher-rated fuse.
• Consumer unit: Check that the relevant MCB or RCD has not tripped. Reset if safe to do so.
• Terminal block: With power isolated, remove the boiler front panel and verify that live, neutral, and earth are securely connected at the boiler terminal block.
• Professional help: If power is present at the boiler but it remains dead, the internal PCB or transformer may have failed and should be tested by a technician.