When a boiler doesn’t ignite there could be a number of reasons for the fault. This guide will discuss the most common faults that can occur and result in a boiler not igniting.

There are also some troubleshooting steps included where it may be safe to try and resolve the matter in person. However, if there are any doubts always call a qualified Gas Safe engineer for assistance.

1. Faulty Gas Valve

A gas valve is the part of your boiler that controls the level of gas that is released through to the boiler’s combustion chamber. The valve opens and closes to control the level of gas that reaches the pilot light and burner however faults can occur with the valve such as blockages or damage to the wire connections.

Unfortunately, it would not be deemed safe to investigate any gas valve issues yourself and should be left to a qualified professional who can investigate the matter further and resolve it safely.

2. Blocked Burner

Another reason that a non-starting boiler can occur could be due to debris blocking the burner inside the unit. Gas boilers produce carbon when in use which can clog up the burner over time.

Again, a specialised engineer will be required to clean the burner or replace it if damage has occurred. Burner replacements can be pricey and therefore depending on the age of the boiler, it may be more worthwhile to replace the entire boiler, benefiting from a modern unit with improved energy efficiency.

If you need to reset your boiler too often, it may be a sign of a more significant fault, such as a faulty PCB, a boiler leak, a central heating pump problem, and if your boiler isn’t firing up the central heating, it may be time to consider getting a new boiler quote.

3. Low Gas Pressure, or no Gas

In the first instance, if you are experiencing gas supply issues it may be worth checking if the gas supply is successfully coming into the property, either by attempting to run another gas appliance such as a cooker, or asking neighbours if they are also facing gas supply issues.

If there is a local issue, contact the emergency gas service.

However, if the matter is not with the gas supply coming into the property, a Gas Safety registered engineer should be contacted to undertake tests to determine the source of the issue.

Issues occur with the gas meter itself or due to fluctuations with the gas pressure, however, either of these matters would need assistance from specialised Gas safe registered engineers.

Boiler brand faults: 

• Common Biasi boiler faults.
• Ariston boiler problems.
• Vokera boiler faults.
• Baxi boiler problems.
• Alpha boiler problems.
• Worcester Bosch boiler problems.

4. Ignition Issues

Faults can occur within the electrode and ignition lead, resulting in the inbuilt safety mechanism to shut down the boiler. The lead creates the spark that enables the ignition of the boiler.

Over time debris can build up inside the lead causing blockages that can prevent the boiler from working properly.

The process of ignition often includes a clicking sound, therefore if the boiler doesn’t start when the clicking sound is occurring, there could be an issue with the electrode and ignition lead.

In this situation, a Gas Safe registered engineer will be required to test the electrode and ignition lead and replace if necessary. Often making repairs to the electrode and ignition lead do not cost-effective and therefore a replacement is the suggested approach.

5. Faulty Fan

The purpose of the fan inside the boiler is to create a draught to push the emissions and gases from the boiler into the flue and then out of the property.

When a boiler detects that the fan is not working, a safety mechanism will shut down the boiler as it could be dangerous to ignite with additional gasses inside.

When in operation, the fan would normally make a slight noise, and therefore if this cannot be heard, a faulty fan may be the reason behind the boiler not starting.

In this scenario, a specialised engineer will be required to confirm the diagnosis and investigate fixing the fan.

A replacement fan can be an expensive part to source and therefore depending on the age of the boiler, options such as reconditioning the faulty fan with a new motor could be explored or ultimately a new boiler may be needed if it is an ageing unit.

Is your boiler losing power? Or is your boiler pressure too high? If your boiler is old, past its warranty, it may be time for a new boiler replacement.

6. No Pilot Light

Inside the boiler, if the electrode and ignition lead is working correctly, this should light the pilot light, however, if the light has gone out, the boiler will fail to start.

Sometimes the jet that a pilot light comes out from can become blocked with debris and a specialised engineer will be required to either clean or replace the pilot light jet. Luckily in this scenario, the replacement parts are fairly cheap.

Other causes of a boiler not igniting

Unfortunately, a boiler may not ignite for many reasons. Common issues to explore before calling a professional are as follows:

• Check the Thermostat setting– The thermostat controls the temperature that the boiler will heat up to. The location of the thermostat can be crucial as if the room
the temperature, where the thermostat is situated, is warmer than the setting, the boiler will not turn on.

• Check the timer clock and programme – A boiler is often set to a programme providing a set routine when the boiler should operate. If the clock or the programme is incorrect, the boiler will not turn on as planned.

• Check the power source and fuse box – Ensure that the programme unit has power. Should the power not be on, also check the fuse box to see if a fuse has tripped for safety purposes or following a power cut for example.

• Prepayment meter – Should a prepayment meter be set up within the property, it would be worthwhile checking that the meter has credit applied to enable the heating system to work.

Related boiler problems:

• How to descale a boiler.
• Boiler overheating.
• What is the age of your boiler? 
• How to balance your radiators.
• Faulty boiler heat exchanger.
• Boiler PCB faults.
• Boiler not igniting.
• No power to your boiler.

Boiler Not Igniting Next Steps

If the basic troubleshooting hints do not resolve the problem, or if the diagnosis is more serious, always seek the advice of a qualified heating engineer for further support.

Should an array of intermittent issues occur with an ageing boiler consider a replacement in advance of winter where possible.