If your boiler is not firing up, the most likely reasons are no gas getting to it, low water pressure, a frozen condensate pipe in cold weather, or the boiler going into ignition lockout after a failed attempt to light. The first three you can check yourself. Repeated lockouts need a Gas Safe engineer.
We’re Clever Energy Boilers, a Gas Safe registered (no. 554138) and Worcester Bosch accredited installer based in Bingley. Our engineers fit boilers across Yorkshire, the North West and the Midlands, and we’ve completed more than 25,000 installations over the past 15 years. This guide explains what’s safe to check, what the common codes mean and when replacing the boiler makes more sense than fixing it.
What should I do if I smell gas?
Don’t try to restart the boiler. Turn off the gas at the meter if you can, open windows and doors, don’t use light switches or anything that could spark, and leave the property. Call the National Gas Emergency Service on 0800 111 999. It’s free and open 24 hours a day.
What can I safely check myself?
Work through these in order. Most no-fire problems are solved somewhere on this list.
- Is the gas on? Check whether your hob or other gas appliances work. If you’re on a prepayment meter, make sure there’s credit.
- Is the boiler getting power? Look for lights on the display and check the fused spur switch next to the boiler.
- Is the heating calling for heat? Turn the thermostat up and make sure the timer is in an “on” period.
- Is the pressure above 1 bar? If not, follow our guide on how to repressurise a boiler.
- Is it freezing outside? A frozen condensate pipe is one of the commonest winter causes. Here’s how to defrost your condensate pipe.
- Is there a fault code? Note it down before pressing anything, then press reset once.
What is boiler ignition lockout?
Ignition lockout means the boiler tried to light, didn’t detect a flame, and shut itself down as a safety measure. It’s doing exactly what it’s designed to do.
You can press reset once or twice. If it fires and keeps running, the cause may have been a one-off, such as a brief interruption to the gas supply. If it locks out again, stop resetting it and call a Gas Safe engineer, as repeated resets won’t fix the underlying problem.
What causes a boiler not to fire up?
Once the simple checks are ruled out, the cause is usually inside the boiler. These all need an engineer, but it helps to know what they might find.
| Part | What goes wrong | Common sign |
|---|---|---|
| Ignition electrode | Worn or dirty, so it can’t spark properly | Clicking with no flame |
| Flame sensor | Can’t confirm the flame is lit | Lights briefly, then cuts out |
| Gas valve | Fails to open | No ignition at all |
| Fan | Doesn’t run, so the boiler won’t try to light | Fan fault code, no fan noise |
| PCB (circuit board) | Electronic fault stops the start sequence | Blank or frozen display |
| Blocked condensate trap | Water backs up and stops the boiler | Gurgling, then lockout |
Our guide to boiler PCB faults explains circuit board problems in more detail. Never take the boiler casing off yourself.
Why is my boiler not firing up for heating but the hot water works?
If the boiler fires for hot water but not for the radiators, it’s not an ignition problem. It’s usually the thermostat, the timer, a diverter valve or a zone valve. Our guide on hot water but no heating covers it.
Why is my Worcester, Vaillant, Ideal or Baxi boiler not firing up?
Each brand shows ignition problems with its own code. Here’s what to look for.
Worcester Bosch
A Worcester that won’t light usually shows EA 227. Our guides to the Worcester 227 code and the EA fault explain it. As accredited Worcester Bosch installers, we can tell you whether an older Greenstar is worth saving.
Vaillant
Vaillant ecoTEC boilers show F28 when ignition fails on start-up and F29 when the flame goes out mid-run. Read our Vaillant F28 guide or see Vaillant boiler installation if yours is getting old.
Ideal
Ideal boilers show L2 for ignition lockout. Our Ideal L2 guide goes through the causes, and our Ideal boiler installation page covers newer models.
Baxi
Many Baxi boilers show E133 when they fail to ignite, often because of a gas supply issue or a frozen condensate pipe. See our Baxi boiler installation page for the current range.
Why is my oil or LPG boiler not firing up?
Check the tank first. Low oil or LPG is the most common reason these boilers won’t fire. Oil boilers also have their own reset button, but if it trips more than once, call an OFTEC or Gas Safe engineer as appropriate. We fit LPG and oil boilers for homes off the gas network.
Should I repair it or replace the boiler?
If your boiler is over 8 years old and has started locking out regularly, replacement is usually the smarter choice. Ignition faults on older boilers rarely come alone, and paying for call-outs on a boiler that’s losing efficiency every year isn’t great value.
We provide boiler replacement at a fixed price, carried out by Gas Safe engineers. You can also protect your new boiler with a long, market-leading warranty arranged through Clever Energy. Many swaps are completed in a single day, and you can spread the cost with boiler finance.
Boiler not firing up FAQs
How do I reset my boiler?
Press and hold the reset button for a few seconds, or turn the dial to the reset position, depending on the model. Only try it once or twice.
Why does my boiler fire up then go out?
The flame sensor may not be detecting the flame, the gas pressure may be low, or the condensate pipe may be blocked. If it happens repeatedly, call an engineer.
Can cold weather stop a boiler firing up?
Yes. A frozen condensate pipe is the main cold-weather cause. Thawing it with warm (not boiling) water usually gets the boiler going again.
Is it safe to keep resetting my boiler?
No. A couple of resets is fine, but if it keeps locking out, something is wrong and it needs a Gas Safe engineer.
