Boiler will not start at all, no lights or display

Safety first: Do not open the boiler casing unless you are competent; live mains parts are present.

• Check other appliances: Confirm that power is available in the property and that other sockets work.
• Inspect fused spur: Replace the 3A fuse in the boiler's fused spur with a new one of the same rating if blown.
• Check consumer unit: Ensure the circuit breaker feeding the boiler has not tripped.
• Check external controls: Make sure any external programmer is powered and switched on.
• Engineer diagnosis: If power is present at the boiler but it remains dead, the engineer should test the main switch, internal fuses, and PCB power supply and replace faulty components.