Boiler Keeps Turning Off or Locking Out?
A boiler that keeps switching off is trying to tell you something. Here are the usual causes and how we fix them for good. Gas Safe (587401), East London. Call 07927 882561.
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Upfront cost — no obligation A boiler that fires up and then cuts out — or keeps locking out and needing a reset — is a common and frustrating fault. The good news is that it’s usually caused by one of a handful of issues, and once the underlying cause is fixed it stops for good. The important thing is not to just keep resetting it, because that ignores whatever is actually triggering the shutdown. Here’s what’s normally behind it.
Low water pressure
Most modern combi boilers will shut down if the system pressure drops too low, as a safety measure. If your pressure gauge reads below around one bar, that alone can cause repeated cut-outs. Topping it up can be a temporary fix, but if the pressure keeps falling there’s usually a leak or a failing part behind it that needs finding — see our [guide on low boiler pressure](https://gas-first.co.uk/low-boiler-pressure/). See: [low boiler pressure](https://gas-first.co.uk/low-boiler-pressure/).
Most modern combi boilers will shut down if the system pressure drops too low, as a safety measure.
Overheating or a faulty thermostat
If the boiler thinks it’s overheating — often due to poor circulation, sludge, a failing pump or a faulty thermostat — it will shut down to protect itself. This can show up as short-cycling, where the boiler fires briefly then cuts out again and again. We diagnose whether it’s the controls, the pump or the system causing it.
If the boiler thinks it’s overheating — often due to poor circulation, sludge, a failing pump or a faulty thermostat — it will shut down to protect…
Frozen condensate pipe (in cold weather)
In winter, a very common cause of a boiler locking out is a frozen condensate pipe — the pipe that carries condensation outside freezes and backs up, tripping the boiler. It’s often something you can thaw yourself, and we can talk you through it on the phone. See our [frozen condensate pipe guide](https://gas-first.co.uk/frozen-condensate-pipe/). See: [frozen condensate pipe](https://gas-first.co.uk/frozen-condensate-pipe/).
In winter, a very common cause of a boiler locking out is a frozen condensate pipe — the pipe that carries condensation outside freezes and backs up…
Ignition, flame or fan faults
If the boiler tries to fire but locks out, it can be an ignition fault, a flame-detection issue, or a fan or airflow problem. These need a Gas Safe engineer to diagnose and repair safely — we read the fault, test the relevant components, and fix the cause so it stops cutting out.
If the boiler tries to fire but locks out, it can be an ignition fault, a flame-detection issue, or a fan or airflow problem.
Frequently Asked Questions
Why does my boiler keep switching itself off?
The most common causes are low system pressure, overheating due to poor circulation or a faulty pump/thermostat, a frozen condensate pipe in winter, or an ignition or fan fault. A proper diagnosis pinpoints which.
Is it safe to keep resetting my boiler?
Resetting once is fine, but if it keeps locking out, repeatedly resetting just masks the real problem. It's better to have the underlying fault diagnosed.
My boiler cut out in cold weather — could it be frozen?
Very likely a frozen condensate pipe, which is common in winter. It can often be thawed safely — call us and we can talk you through it.
Can you fix a boiler that keeps cutting out?
Yes. We diagnose the underlying cause and repair it so the boiler runs reliably again, with a clear quote before any work.
What Our Customers Say
Rated 5 stars by homeowners and landlords across East London
“Highly recommend for any boiler issues. We used them for our annual service and to fix several other issues. The engineer was incredibly thorough, he even took the time to overhaul the system. It's rare to find an engineer who is this transparent and knowledgeable. Fair pricing and excellent communication throughout. Will definitely use them again next year and any time we need them.”
Josh Uddin | East London
“Boiler installation was professional and efficient.”
Nazmin Begum | Barking, East London
“They did the job on time, very prompt and professional. Came and installed our gas cooker in Dagenham. Highly recommend to anyone looking.”
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