If your boiler keeps turning off, it’s nearly always shutting itself down for protection. Low pressure, a frozen condensate pipe, a gas supply problem, a lost flame or overheating because water isn’t moving round the system are the usual triggers. Unlike short cycling, the boiler doesn’t fire straight back up. It stays off until the cause clears or someone resets it.
We’re Clever Energy Boilers, Gas Safe registered (no. 554138) and accredited Worcester Bosch installers based in Bingley. Our engineers have completed more than 25,000 installations across Yorkshire, the North West and the Midlands over 15 years, from Bradford and Leeds to Halifax and Keighley. This guide matches when your boiler cuts out to the likely cause, then covers the checks you can safely make and the point where replacing it makes more sense than another repair.
What should I do if my CO alarm goes off?
Leave the property straight away and call the National Gas Emergency Service on 0800 111 999. The same applies if you smell gas. Don’t stop to reset the boiler.
Is my boiler turning off or short cycling?
They get mixed up a lot, but they’re different faults with different causes:
- Turning off means the boiler shuts down and stays off, usually to protect itself from overheating, low pressure or a lost flame.
- Short cycling is rapid on and off firing every few minutes, and an oversized boiler or a badly placed thermostat is normally behind it.
Quick bursts on and off belong in our boiler short cycling guide. If yours shuts down and stays down, read on.
Boiler cutting out at a glance
When your boiler turns off tells you a lot about why. Find the row that matches what you’re seeing:
| When it cuts out | Most likely cause | Where to go next |
|---|---|---|
| On start-up, after trying to light, with a lockout code | No flame detected, often a gas supply problem | Boiler ignition lockout |
| Mid-run, after working for a while | Low pressure, or a failed pump letting the boiler overheat | Boiler losing pressure |
| Mid-run, with gurgling or cold radiators | An airlock or sludge in the system | Boiler airlock |
| In frosty weather | A frozen condensate pipe | Defrost your condensate pipe |
| While you’re running hot water | Low pressure or a faulty valve | Faulty diverter valve |
| Every few minutes, then fires again on its own | Short cycling | Boiler short cycling |
| Heating goes off at odd times, no fault code | Thermostat settings, batteries or a sensor fault | Boiler thermostat not working |
| A combi fires briefly with no taps on | Normal pre-heat | Nothing to fix |
| Different fault codes each time | Several parts failing at once | When to replace a boiler |
A boiler that won’t come on at all, rather than starting and then cutting out, is a different problem. Our guide to a boiler not firing up is the better place to start.
Why does my boiler keep turning off?
These are the causes in more detail, starting with the ones you can check yourself.
Has the pressure dropped below 1 bar?
Below 1 bar, the boiler can shut itself down. Look at the gauge on the front, and if it’s low, top it up to about 1.5 bar using our step-by-step guide on how to repressurise a boiler. Needing to do that every week or two means a leak or a faulty part somewhere, and our guide to a boiler losing pressure shows where to look.
Is the condensate pipe frozen?
In a hard frost, the outside section of the condensate pipe can freeze. Water backs up into the boiler and it switches itself off. Thaw the pipe with warm water, never boiling, then reset the boiler once.
Homes on the exposed Pennine hillsides around Queensbury and Thornton tend to see this first when the temperature drops. Our condensate pipe guide explains how the pipe works.
Is gas getting through?
If the gas stops, the flame goes out and the boiler shuts down. Check a prepayment meter still has credit and that your other gas appliances work. A flame code on the display points to a lockout, and our boiler ignition lockout guide lists the codes for each brand.
Could it be the thermostat or a sensor?
Flat batteries in a wireless room thermostat, a lost connection or the wrong schedule can all switch the heating off when you don’t expect it. Inside the boiler, a faulty temperature sensor can make it think it’s overheating. The room thermostat you can check yourself. A boiler sensor needs a Gas Safe registered engineer.
Has the pump failed?
When the pump stops moving water, the water in the boiler gets too hot and a safety device shuts it down. Pump replacement is an engineer job, and our guide to a boiler pump not working covers the signs.
Is there air or sludge in the system?
Trapped air or a build-up of sludge slows the water down, so the boiler overheats and cuts out. Bleeding the radiators can clear air, and our guides to a boiler airlock and bleeding radiators walk you through it. Sludge usually needs a flush, and a magnetic filter helps keep it out afterwards.
Is a valve sticking?
A sticking or failing valve inside the boiler can upset the flow of water and shut it down. On a combi that cuts out mainly when you run a hot tap, the diverter valve is a common suspect. Our faulty diverter valve guide explains the signs.
Is the heat exchanger blocked or damaged?
If it is, heat can’t pass to the water properly and the boiler overheats. It’s one of the bigger repair bills. Our guide to a faulty heat exchanger covers the warning signs.
Is your combi just pre-heating?
Quite possibly. Some combis fire briefly on their own to keep a small amount of water warm, so hot water reaches the taps faster. A short burst with no fault code is the boiler working as it should.
What can you safely check yourself?
- Look at the pressure gauge. Below 1 bar, top it up to about 1.5 bar.
- Write down any fault code before you press anything. It narrows the cause down, and an engineer will want it.
- Check the condensate pipe in frosty weather and thaw any ice with warm water.
- Try the thermostat. Change the batteries and make sure the settings and schedule are right.
- Bleed your radiators if they’re cold at the top, then check the pressure again.
- Reset once. Glow-worm advises a single reset, and if the boiler cuts out again, leave it for a Gas Safe registered engineer.
Never take the casing off or try to fix anything inside the boiler yourself.
Is it dangerous when a boiler keeps turning off?
Not usually. A shutdown is the boiler protecting itself from overheating, low pressure or a lost flame. The exceptions are a CO alarm sounding or a smell of gas, and both mean leaving the property and calling 0800 111 999.
What does it cost to fix a boiler that keeps turning off?
Typical UK costs for the parts that most often cause it:
| Repair | Typical UK cost |
|---|---|
| Pump | £150 to £380 |
| Gas valve | £180 to £220 |
| Heat exchanger | £400 to £600 plus labour |
| PCB | £300 to £600+ |
If the circuit board is to blame, our guide to boiler PCB faults explains what’s involved.
Should I repair it or replace the boiler?
On a younger boiler with one clear cause, a repair usually makes sense. The pattern to watch for is an older boiler that shuts down again and again with a different code each time. On a boiler of 8 years or more, that usually means several parts are failing at once. You fix the pump, then the valve goes, then the board.
A boiler replacement swaps that run of call-outs for one fixed cost and a more efficient boiler, with long, market-leading warranties available through Clever Energy. You can spread the cost with boiler finance, and our guide to how much a new boiler costs sets out typical prices.
Cutting out on Worcester, Ideal, Vaillant and Baxi boilers
Worcester Bosch
A Worcester that overheats, often because water isn’t moving, can lock out with an E9 overheat fault. EA 229 means the flame was lost while it ran, and a blocked condensate trap can cause it, as our Worcester 229 guide explains. If it won’t come on at all, see Worcester boiler not turning on. Our Worcester Bosch boiler installation page covers the current range.
Ideal
Ideal shows L2 for an ignition lockout and F2 for flame loss. Our Ideal boiler fault codes guide goes through the rest, and the Ideal boiler installation page has the newer models.
Vaillant
A Vaillant that shuts down on low pressure usually shows the F22 fault code, while F.29 means the flame went out mid-run (our Vaillant F29 guide has the detail). One that has stopped with nothing on the display is covered in Vaillant boiler not working with no fault code. If yours is getting on, have a look at Vaillant boiler installation.
Baxi
Baxi links its E133 code to the gas supply, the ignition or flame, or a blocked condensate pipe. Our Baxi E133 guide and Baxi boiler error codes guide cover it, and Baxi boiler installation shows the current models.
Boiler keeps turning off FAQs
Why does my boiler turn off after a few minutes?
Usually low pressure, a failed pump or an airlock, with the boiler shutting down to stop itself overheating. If it switches off and back on every few minutes, that’s short cycling, which has different causes.
Why does my boiler turn off when hot water is running?
Low pressure or a faulty valve, most often the diverter valve on a combi. Check the pressure first, then get a Gas Safe registered engineer if it keeps happening. Our guide to combi hot water going cold covers a related problem.
Is it normal for a combi to fire on its own?
Yes. A brief firing with no taps running is often the pre-heat keeping water warm, and it’s only a concern if a fault code comes with it.
Why does my boiler cut out in cold weather?
Most often a frozen condensate pipe. Thaw it with warm water and reset once, following our guide to defrosting a condensate pipe.
Should I keep resetting it?
No. Glow-worm advises one reset, and if the boiler cuts out again the fault is still there. Our 10 most common boiler problems guide is a good next read.
Get a new boiler with Clever Energy
We install new boilers in Bingley, Bradford, Leeds, Halifax, Keighley, Huddersfield and across Yorkshire, the North West and the Midlands, from Manchester and Liverpool down to Birmingham and Leicester. Start with our boiler installation page, or compare Worcester Bosch, Vaillant, Ideal and Baxi installation. Get a fixed price online without waiting for a home visit, or request a callback and we’ll ring you. Afterwards, a Clever Care plan keeps your new boiler protected.