Furnace will not start, no lights or display, completely dead

Safety: Do not remove the appliance cover unless you are competent. Isolate power before touching any wiring.

User steps:

• Check that the wall isolator switch is turned on.
• Inspect the consumer unit for a tripped breaker and reset if appropriate.
• Check and replace the fuse in the fused spur with the correct rating if blown.
• Ensure any external timeclock or programmer is powered and set to ON or a timed period.

Technician steps:

• Verify mains voltage at the appliance terminals.
• Test the appliance on/off switch and replace if faulty.
• Inspect internal fuses on the Glow-worm PCB and replace only with identical types if blown, after finding the root cause.