"Boiler not working" covers a lot of different problems, and the right first step depends on exactly what you're seeing. Pick the description that matches your situation below, or call us directly if you'd rather just describe it over the phone.
A few quick things worth checking first
Before anything else, these three checks resolve a surprising number of "boiler not working" callouts, and they're safe for anyone to do:
- Check the pressure gauge. If it's reading below 1 bar, low pressure is very likely your answer — see our losing pressure page.
- Check your thermostat. Make sure it's calling for heat, set above room temperature, and that batteries (if it's wireless) aren't flat.
- Check your electrics. A tripped fuse or switched-off fused spur will stop a boiler dead — check your consumer unit and any isolation switch near the boiler.
If none of that explains it, don't keep experimenting — especially with anything involving the boiler's casing, gas connection, or flue. That's exactly what we're for.
What we test when we arrive
Every diagnosis follows the same discipline as our emergency callouts — our advice article on what we check on every callout covers it in full, but in short: the engineer confirms the boiler is getting power, gas and pressure, then works through the fault methodically — gas tightness where anything gas-side is suspected, inlet working pressure, a flue combustion check where relevant, electrical safety checks, and testing of the individual components the symptoms point to. The point is a confirmed cause, not a guess from the error code alone.
Likely repairs
What actually gets replaced depends entirely on what the diagnosis finds — but across "boiler completely dead" callouts, the usual suspects are ignition components, a failed fan or its pressure switch, a faulty PCB, a seized pump, or something as simple as a failed external control or fuse. Whatever it turns out to be, the part is quoted before fitting and most repairs carry a 12-month parts warranty. For a sense of how we work through a stubborn fault, see the Ariston Evo we traced to a blocked plate heat exchanger in Stourbridge in our case studies, or the Greenstar Ri in Walsall that two engineers had written off and that needed a gasket and an electrode.
Prefer to narrow it down yourself first? Our Boiler Problem Finder walks through each symptom, and we've got dedicated guides for a boiler that keeps switching off and a boiler making strange noises.
Frequently asked questions
My boiler won't turn on at all — what should I check first?
Three things, all safe: the pressure gauge (below 1 bar can stop a boiler dead), the thermostat and its batteries, and your electrics — a tripped fuse or switched-off fused spur near the boiler. Those three resolve a surprising number of "boiler not working" callouts before anyone travels.
Should I keep pressing the reset button?
One reset, following your manual, is fine. If the boiler locks out again, stop — repeated resets don't fix anything and can make some faults worse. That's the point where it needs a proper diagnosis.
What does the £99 diagnosis actually get me?
A Gas Safe engineer, the first hour of work, and a confirmed answer on what's wrong. If a part is needed it's quoted before fitting, and if the honest answer is that repair isn't worth it, we'll say so.
Can you fix it on the first visit?
Usually — the van carries the most commonly needed spares, and across 505 repairs since October 2023, 88% were finished on the first visit. Where a brand-specific part has to be ordered, we tell you before anything is agreed.