Boiler won't fire up? Why it won't light and what to check
Updated 7 November 2026
When the heating comes on, a modern boiler starts its fan, sparks an igniter, opens the gas valve and checks for a flame. If it doesn't see a flame within a few seconds, it tries again, and after a few failed tries it locks out and shows a fault. Where it stops in that sequence is a good clue to what's wrong.
If you can smell gas, don't try to relight anything. Call 0800 111 999.
Nothing happens at all
No lights, no display, no fan: that's power, not ignition. Check the switch near the boiler, its fuse and your fuse box. Our boiler not working checklist goes through it.
It clicks but won't light
The igniter is sparking but there's no flame, which usually means gas isn't getting through.
- Try the hob if you have a gas cooker. If that won't light either, the problem is your supply, not the boiler.
- Check the lever by your gas meter. When the handle lines up with the pipe, the gas is on.
- On a prepayment meter, check the credit. Some meters need a button pressing to turn the supply back on after you top up.
If the gas is fine, the likely culprits are the ignition electrode, its lead or the gas valve. Those need an engineer.
It lights, then cuts out
If the flame comes on and goes out after a few seconds, the boiler isn't detecting it properly, or something is shutting it down. Common causes are a dirty or worn flame sensor, a blocked condensate trap or pipe, or a problem with the flue or fan. In freezing weather, check for a frozen condensate pipe first, especially if the boiler gurgles.
It shows a fault code
Ignition faults show up as codes like EA on a Worcester Bosch, F28 on a Vaillant, E133 on a Baxi or L2 on an Ideal. Our fault codes guide explains them. Check the pressure gauge too: if it's dropped below 1 bar, the boiler may refuse to fire.
Older boilers with a pilot light
Some older boilers keep a small pilot flame burning. The relighting steps are often printed inside the front panel or in the manual. If the pilot won't stay lit, a part called the thermocouple has probably worn out, which is usually a quick repair for an engineer.
Reset once
Once you've checked the gas, the pressure and the condensate pipe, press reset once. If it locks out again, leave it, as resetting over and over can make some faults worse. Note any code and ring us, and a local Gas Safe engineer will call you back with a price.
Need it sorted? Boiler repair in Newcastle typically costs £150 to £450. A local engineer will give you a price before starting.