Why is my boiler not igniting? Common causes and fixes
There’s nothing worse than waking up to a cold home and discovering your boiler hasn’t come on. If your boiler isn’t igniting, don’t panic just yet. There are several reasons why this might be happening, and in many cases, a simple fix by a heating engineer could get your heating and hot water back up and running in no time.
Common reasons your boiler isn’t igniting
1. Faulty fan or airflow issues
One of the reasons your gas boiler won’t ignite is a faulty fan. The fan ensures safe expulsion of waste gases, and if it’s not working properly, the boiler won’t ignite for safety reasons.
Signs of a faulty boiler fan:
- No usual whirring sound before ignition.
- Fault code on the display (check your manual)
- No airflow detected in the flue system.
If you suspect a fan issue, contact a Gas Safe registered engineer.
How to test a boiler fan
If you think your boiler’s fan might not be working, you can conduct some basic checks before calling a Gas Safe Registered Engineer.
- Listen for noise: When the boiler attempts to ignite, you should hear a whirring sound from the fan.
- Check fault codes: Many boilers will display a fault code if the fan is malfunctioning. An F28 or F29 boiler fault could indicate possible flame failure or an ignition issue – check your manual or our list of codes.
If you suspect a fan issue, contact a Gas Safe registered engineer.
2. No gas supply
If your gas supply is interrupted, your boiler won’t ignite. Check if other gas appliances, such as your hob, are working. If not, there may be a gas supply issue. If you suspect an issue with your gas supply, contact your supplier.
Alternatively, if you smell gas, you need to act quickly. Turn off your gas supply, do not switch on any light switches, don’t turn on any electric appliances, open windows, and leave your home. When outside, call the National Gas Emergency Services on 0800 111 999.
3. Low system pressure
Low system pressure can affect heating performance; if the pressure is too low (below 1 bar), the boiler may fail to ignite.
How to check and fix low pressure:
- Locate the pressure gauge on your boiler.
- If below 1 bar, follow instructions in your manual to repressurise.
- Check out our repressurising guide for more help.
4. Ignition or pilot light issues
Modern gas boilers use electronic ignition, meaning they don’t have a standing pilot light like older boilers. However, ignition system failures can prevent your boilers from firing up.
Common causes include:
- Faulty spark electrode.
- Blocked burner.
- Ignition PCB issues.
If simpler checks don’t resolve it, an engineer should inspect the ignition components.
5. Frozen condensate pipe
When winter takes hold, boilers can sometimes stop working because of a frozen condensate pipe, triggering an F28 fault code (F1 or F4 for older Glow-worm appliances). This can leave you without heating or hot water when you need it most.
During colder months, your boiler’s condensate pipe can freeze, causing a blockage and preventing ignition .
How to fix a frozen pipe:
- Locate the external condensate pipe.
- If frozen, pour warm (not boiling) water over it to thaw the ice.
- Reset the boiler and try again.
When to call a professional
If your boiler still won’t ignite after these checks, it’s time to call a Gas Safe Registered engineer. Issues like a faulty fan, ignition failure, or gas supply problems should always be handled by a professional. At Glow-worm, we understand how important reliable heating is. Visit our advice pages for more information, or get in touch with a certified engineer to restore warmth to your home.