Boiler completely dead, no display or lights at all (all brands)
⚠️ This needs a qualified professional
This fault involves gas or mains electrical work. Don't attempt a DIY repair — UK law requires gas work to be carried out by a Gas Safe registered engineer. Below is what to check and describe to them, not step-by-step repair instructions.
A boiler that’s completely dark — no display, no lights, nothing at all — is a genuinely different situation from a boiler showing a fault code, and worth ruling out a simple power issue before assuming a serious fault.
What’s safe to check yourself
- Check the boiler’s own on/off switch (often on the boiler itself or a nearby fused spur switch on the wall) is genuinely switched on.
- Check the fuse in the fused spur switch, if fitted (similar to a plug fuse) — a blown fuse is a common, harmless-to-check cause of total power loss.
- Check your consumer unit/fuse box for a tripped circuit breaker on the boiler’s circuit.
- Check whether anything else in the house has also lost power at the same time, which would point to a wider electrical issue rather than something specific to the boiler.
⚠️ This needs a Gas Safe engineer
Beyond checking the switch, fuse, and circuit breaker, don’t attempt to open the boiler casing or investigate further yourself. If power checks all come back fine and the boiler is still completely dead, the internal control board or transformer has likely failed — this needs a Gas Safe registered engineer to diagnose and repair.
Some links on this page are affiliate links. We may earn a small commission at no extra cost to you.