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A boiler with a completely blank display hasn't necessarily broken down — it has lost power. Here is a safe, homeowner-friendly checklist for tracking down where the supply has been interrupted, plus the point at which a dead boiler means it's time to call an engineer.
It's worth separating two things that look similar but are very different. A lockout leaves the display lit, usually flashing a fault code or warning light — the boiler has power but has shut the burner down for safety. A blank, dead display with no lights at all means electricity isn't reaching the boiler's controls. There's nothing to reset, because the brain of the boiler is switched off.
The good news is that the most common reasons for a totally dead boiler are electrical supply issues you can safely check yourself — a tripped switch, a blown fuse or a tripped breaker — none of which involve opening the boiler or going anywhere near the gas side. If you'd otherwise expect the boiler to be on (the heating or hot water is calling for it), work through the checklist below in order.
If you can smell gas, stop. A blank display is an electrical symptom, not a gas one — but if you ever smell gas, don't touch any electrical switches (including the fused spur), open the windows, leave the property and call the National Gas Emergency line on 0800 111 999.
Almost every domestic boiler is wired to a fused spur (also called a fused connection unit) rather than a normal plug. There's usually a switch close to the boiler — often in a kitchen cupboard, the airing cupboard, or on the wall beside it — that turns the boiler's supply on and off. It's easy for one of these to be knocked off accidentally while you're reaching for something, or switched off by a cleaner, decorator or previous engineer who forgot to switch it back.
Find that switch and check it's set to on. Some fused spurs have a small neon light that glows when live, which is a handy indicator. If flicking it on brings the display back, you've solved it.
If the switch is on but the boiler is still dead, the next suspect is the fuse. People often ask "where is the fuse for my boiler?" — and the answer is that it usually lives inside the fused connection unit (the fused spur) that feeds the boiler, not in your main consumer unit. The fuse sits behind a small carrier on the front of the spur, which you can pop out with a flat screwdriver. Boiler spurs are commonly fitted with a 3A fuse.
With the supply switched off, you can take the fuse out and check it. A blown cartridge fuse sometimes shows a visible break in the wire, though not always. If you have a like-for-like replacement (same amp rating), fitting a fresh fuse is a homeowner-safe job. If the new fuse blows again straight away, stop — something downstream is faulty and needs an electrician or, if it's the boiler itself, a Gas Safe registered engineer.
Replace like for like. Don't fit a higher-rated fuse to "stop it blowing". The fuse rating is chosen to protect the wiring and the appliance. A repeatedly blown fuse is a warning sign to be investigated, not bypassed.
If the spur and its fuse are fine, head to your consumer unit (fuse board). Look for any switch that has tripped to the off position — this could be an individual circuit breaker (MCB) for the kitchen or boiler circuit, or a larger RCD that has cut several circuits at once. If you find a tripped switch, you can reset it by firmly switching it back to on.
If it immediately trips again, don't keep forcing it — a breaker that won't stay on is detecting a genuine fault, and that needs a qualified electrician (or, where the fault is in the boiler, a Gas Safe engineer) to trace. While you're there, rule out a wider problem by checking whether other appliances on the same circuit have power.
A minority of boilers — often older installs or some system setups — are wired to a standard 13A plug and socket rather than a fused spur. If that's you, check the plug is pushed fully in, the socket switch is on, and the socket itself works by testing it with another appliance. The fuse in this case is the one inside the plug (typically a 3A fuse for a boiler), which you can check and replace the same way as a spur fuse.
If you've confirmed power is genuinely reaching the boiler — the spur is switched on, its fuse is intact, the breaker is up, the socket works — but the display stays blank and the boiler shows no signs of life, the problem has moved inside the boiler. The most common culprit at this point is the printed circuit board (PCB), the boiler's main control board. A failed PCB, or a fault in the boiler's internal wiring or transformer, will leave it dead even with a perfect supply.
This is the line you don't cross. Diagnosing or replacing a PCB means opening the boiler casing and working inside a gas appliance, which is strictly a job for a Gas Safe registered engineer. Don't remove the casing yourself. A PCB is also one of the pricier parts to replace, which is exactly where having cover in place can make the difference between a manageable claim and an unwelcome bill.
A note on terminology: any engineer who opens up your boiler must be on the Gas Safe Register (gassaferegister.co.uk) and able to show you their ID card. The old "CORGI" scheme was replaced by Gas Safe in 2009, so a tradesperson still trading on the CORGI name is out of date.
Work through the homeowner-safe checks above first — most dead-boiler call-outs turn out to be a switched-off spur or a blown fuse. Book a Gas Safe registered engineer if:
If the boiler does come back to life but then misbehaves, our guides on a boiler that isn't working and a boiler that keeps cutting out cover the next steps.
A dead boiler that turns out to be a PCB or internal electrical fault is the classic case for having cover in place — the engineer's call-out and the part can both be covered, rather than landing on you as a one-off bill. If you're weighing it up, see what boiler cover actually includes and our run-down of the best boiler cover and cheaper options. Still on the fence? Our piece on whether boiler cover is worth it lays out the trade-offs.
Compare boiler cover plans side by side — including breakdown repair, parts like the PCB, annual servicing and call-out limits — and find a policy that fits your boiler and budget.
Compare boiler coverFor most boilers it's inside the fused connection unit (the fused spur) that feeds the boiler — behind a small carrier on the front of the spur, commonly a 3A fuse. If your boiler is plugged in instead, the fuse is the one inside the 13A plug. It's normally separate from your main consumer unit.
A blank, unlit display means the boiler has lost its electrical supply rather than locked out. Check the fused spur switch, the fuse in that spur, your consumer unit (MCB/RCD), and the plug or socket if it's plugged in. If power is reaching the boiler but it stays dead, the fault is likely internal — most often the PCB.
You can safely check the supply: switch the fused spur on, replace a blown fuse with the same rating, and reset a tripped breaker. What you must not do is open the boiler casing or work on internal parts. If a fuse or breaker keeps blowing, or the boiler is dead despite having power, call a Gas Safe registered engineer.
As an indicative 2026 guide, a replacement PCB typically runs from around £250 to £600 or more once parts and labour are included, depending on the boiler. Costs vary by brand and engineer, which is one reason many people take out cover that includes parts like this.
Yes. After a power cut the boiler should normally come back on its own, but the cut can sometimes trip a breaker or, less often, blow a fuse. Run through the checklist above. If everything looks fine and the display is still dead, treat it as a likely internal fault and book an engineer.