Boiler Not Igniting? Here’s Why!

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Last updated: October 31, 2023

With some appliances around our homes, it can take weeks to notice any faults that may arise. Faults to do with our boilers, on the other hands, are detected almost instantly. Although we often forget that our boiler even exists most of the time, it’s catastrophic when it fails to ignite, leaving you helpless in a freezing cold house with no warm water to speak of.

Don’t worry – we’re here to help. As this problem must be solved immediately to stop your teeth from chattering, our article firstly analyses the reasons why boilers fail to ignite, accompanied by what else can cause a boiler ignition failure. To finish, we’ll guide you through the steps regarding how to ignite a gas boiler safely and effectively. Read on below to find out more1

Reasons Why Boilers Fail To Ignite

Before we dive into how to ignite your gas boiler, it’s firstly important to take a look at why your boiler problems have originated in the first instance. Let’s discuss a few explainable instances as to why your boiler isn’t igniting:

A fuse has tripped

For your sake, we hope that a tripped fuse is the reason why your heating has temporarily gone. A tripped fuse is undoubtedly a simple fix. In most instances, a circuit breaker tripping occurs when the system overloads due to an unusual surge of energy. Remember; it’s important to note that if your fuse continues to trip, this could indicate that there’s an underlying issue within your boiler system. In most cases, however, it’s an easy fix!

Locate the breaker/ fuse box: The majority of breaker boxes are located in the cupboard right beside the front door. Otherwise, you should find them close to the front door wall.

Look for the tripped switch: Opening up your breaker box, ferret out the flipped circuit switch. This switch may not be completely turned off, but between the on and off buttons.

If you found the switch in the middle of the on and off positions, flick it off before turning it back on again. Train your ears for a clicking noise that indicates it’s back on and that power has returned to your system.

A fuse has blown

Most likely due to a surge of power, your boiler’s fuse may have blown.

In order to tell whether the fuse wire has blown, you’re going to have to get up close and personal with the fuse box. As clarified above, this box should be located in the cupboard near the front door or close to the front door wall. A visible gap in the wire or a dark or metallic smear inside the glass indicates that the fuse has indeed blown and must be replaced.

Replacing a blown fuse is a simple process. Noting the fuse amperage and voltage ratings that should be marked on the fuse itself, it’s imperative that you buy the exact same size and what type of fuse it is. Another important point to note is that all equipment should firstly be disconnected from any electrics in the flat. Fuses are ridiculously cheap, so we hope for your sake that this is the solution to all your boiler problems!

Your boiler burner is blocked

If carbon has become clogged up in your boiler’s burner, you may find your heating system stops working altogether. As the boiler component that provides the heat input for a gas appliance through combusting a fossil fuel with air or oxygen to create heat, if your boiler’s burner doesn’t work, your heating system probably won’t either

Eradicating any carbon build-up in the burner should solve any issues. However, this fix is only possible if your burner hasn’t been damaged as a result. If you notice your boiler burner is indeed looking frayed, the first steps you should take are identifying whether it still has any warranty left. Burner replacements are a notoriously expensive part of heating systems, so you want to exhaust every other possible alternative before searching for other burner replacements.

Your home doesn’t need any more heat

Could it be that your boiler hasn’t actually stopped working but is actually so smart, it’s saving energy for you by temporarily turning off? During boiler installations, many homeowners tend to set their home temperature to their own preferences. Say you set yours to 23 degrees, for example. If your boiler’s thermostat settings are working efficiently, then your home won’t be heated beyond this temperature. Therefore, if your home was exceeding this temperature at 23.5 degrees, then your boiler simply won’t turn on.

Fixing this temporary problem couldn’t be easier. All you’ve got to do is tamper with the thermostat settings, increasing the heating setting higher. If you feel the radiators start to turn on, you’ve found your solution.

Check out our review of: Nest Vs Hive: Which Is The Best Smart Thermostat

Low pressure

Another reason your boiler is failing to ignite could be that the gas or water pressure is too low. Regarding gas pressure, this could be a problem with the gas supply around the area or with the sealed system boiler itself. Gas networks are usually very responsive online with concern to possible issues with gas supplies, so head over to your gas supplier’s website or give them a ring to find out if your problems are shared by others in your area.

If there are no problems in your area, you must check the pressure gauge on the front of the boiler. If this pressure gauge reads below one bar, this indicates that water has been lost from the system that must be replaced. Re-pressurising your boiler is a fairly easy fix and can be achieved by carrying out the following instructions inspired by experts over at British Gas:

1 Switch off your boiler at the mains and allow it to cool down

2 Check that both ends of your boiler’s filling loop (the pipe that connects your cold water pipe to the boiler) are attached

3 Opening both valves, allow cold water from the mains to trickle into your system. Remain patient until the pressure gauge reads 1.5 bars.

4 Carefully close both values in turn

5 Turn the boiler on. If nothing happens, press the reset button

6 Remove the filling loop, catching any water spillage. Keep it stored until next time! If this process fails, it’s in your best interests to call a Gas Safe registered engineer to fix the problem once and for all.

Related Post: Best Digital Gas Manometer

Your boiler’s fan is broken

Boiler still not igniting? It could be that the fan within your boiler is broken In order for the hot water and central heating system to work, the fan must generate a draught to push harmful gases from the flue. In fact, the boiler fan works before anything else in the system to generate heat.

The average boiler fan lasts between five to eight years – that’s half the lifespan of the boiler itself – so consider this to be just another cost of buying a new boiler at the time. Plus, there are many DIY hacks you can carry out yourself to check whether your boiler fan is working.

Old boiler fans

The first part of troubleshooting your fan is simply by listening to it! If all you can hear is the fan squeaking, that noise is coming from the fan’s bearings, thereby indicating that something is wrong. Using your screwdriver, move the propeller to get it moving again. Checking an old boiler fan’s hoses is also another hack, as there may be a blockage stopping the air from seeping through naturally. Finally, you can check your old fan’s resistance if you’ve got a multimetre lying around your home.

New boiler fans

On a modern fan appliance, a tachometre tells you how much rotation speed your fan is giving out. Likewise, it will communicate both the actual speed of the fan and the target speed of the fan. For example, say the target fan speed is 5000 revolutions per minute, whereas the actual fan speed is only 2000. In this instance, your boiler fan should display one of the error codes, so head over to your instructional manual to identify what’s wrong.

Plumber fixing electric water heater

What Else Can Cause A Boiler Ignition Failure?

If you’ve tried out the above reasons as to why your boiler is failing to ignite to no avail, another more serious fault may be at play.

Ignition lockout

Otherwise referred to as boiler lockout, ignition lockout is industry-speak meaning that the boiler has shut down so further damage does not occur to its system. There are a number of variables that could cause in boiler lockout, including low or high water pressure, a lack of electricity, no gas supply, or a blockage in the system. Although it’s extremely aggravating when boiler lockout occurs, know that this is your boiler’s way of protecting itself against any further faults.

Luckily, most boilers boast a reset button on the front of the boiler that can be pressed to stop the lockout. Before you do so, however, note down the error code that should flash up on the display unit on the front of your boiler. Once jotted down, consult your boiler’s instruction manual for boiler error codes to find out what fault is responsible for this ignition lockout.

If you cannot seem to find the fault code, simply try resetting your boiler. This can be achieved by pressing down the reset button and holding it down for approximately ten seconds. Then, after waiting two to three minutes, the boiler should be up and running again in no time. If you’re struggling with your boiler not firing up the first time around, repeat this process a couple of more times before giving up.

Electrode and ignition lead

Haven’t had any luck with the reset button for your boiler repair? Ignition lockout may have occurred due to electrode and ignition lead problems. Gas-related issues pertaining to problems with the ignition lead and electrode will create intermittent operation, such as the boiler turning on for only a few seconds to turn back off again.

Your gas valve controls are faulty

As the part of machinery that controls the amount of gas that flows into the boiler for burning, a gas value is one of the most essential components of a boiler. If you alter your central heating needs to allow for more gas to flow into a damaged or blocked valve, the gas cannot enter the chamber, thereby hindering the ignition of your boiler.

Similar to a boiler fan, sorting out the gas value controls cannot be carried out without the help of a Gas Safe registered engineer. Hopefully after a little cleaning and maintenance, your boiler will be up and running again in no time!

How to Ignite a Gas Boiler

If all quick fixes fail, then igniting a gas boiler is contingent on sorting the boiler’s pilot light. The pilot light is a small blue flame responsible for igniting the gas provided to the boiler. In short, this one tiny element is responsible for providing the heating in our homes. With concern to older gas appliances that work thanks to a pilot light, if the pilot light fails to work or goes out, then a dangerous accumulation of gas will still continue to feed through. We cannot emphasise enough that this boiler problem need fixed immediately. Even a pilot light being out of adjustment can engender the production of carbon monoxide gas.

Before attempting to relight the pilot light on your boiler, you should first of all refer to your boiler’s own instruction manual. In conjunction with the following steps, you should succeed:

Both the gas control value and the gas appliance itself should be turned off. If you have any other gas appliances, turn them off too – you don’t want anything to go wrong when carrying out this process.

Be patient for approximately ten minutes. A fault dealing with gas pressure can be dangerous, so waiting for this recommended time period means all gas in the system is able to disperse.

Now that you’ve allowed time for the gas to disperse. remove the gas appliance’s door. Now, turn the gas to “pilot”.

Press the reset switch down for on minute whilst simultaneously holding a flame to the pilot light. Only once the pilot light has ignited should you hold the reset switch down in order to lessen the chances of gas accumulating once again.

Release the reset switch. If your pilot light is out, this means igniting it has failed and professional help from a registered gas engineer is required. If the flame remains lit, however, this means that your efforts have been successful!

Fit the appliance’s door back on and turn the gas back from “pilot”.

WARNING: Never try to relight the boiler if any part of the pilot light – or any part of the boiler, that is – has been submerged n water. The same rule goes for if you smell gas! Even if you detect the faintest gas odor, call the fire department immediately. Even you don’t believe there’s a chance of your boiler over-pressuring, it’s better to be safe rather than sorry.

Above all else, it’s important that you remain safe when working with a thing as dangerous as gas supply. That’s why at this point, your next step should be contacting a Gas Safe Registered engineer. Although the cost of hiring one is expensive –estimated between £30 to £100 per hour – their call out charge is more than worth it for working heating and hot water.


  1. How to fix a boiler that won’t ignite – Viessmann
  2. What to do if your boiler loses pressure – British Gas