Why Won’t My Boiler Ignite? Reasons Why & How To Fix Them Re August 7, 2020

Why Won’t My Boiler Ignite? Reasons Why & How To Fix Them

Boiler turning off

You know it’s not going to be a good day when you wake up and your home feels much colder than usual or you jump straight into a cold shower without checking it’s warm first. So you look at your boiler and it’s flashing red at you, you check the error code (probably on the WarmZilla site) and find that there’s a problem with the boiler ignition. But why? Why won’t my boiler ignite?!

If there is an issue with your boiler it will lockout as a safety precaution and won’t ignite until the issue has been sorted.

In this article, we will look at reasons why your boiler won’t ignite and steps you can take to diagnose (and hopefully fix) the issue before you need to call out a Gas Safe engineer to take a look.

Check the basics first

Some of these suggestions may sound a bit obvious but you’d be surprised at some of the reasons we’ve seen over the years for why boilers won’t ignite, so it makes sense to just cross off the basics first before looking at more serious issues.

Check the gas supply to your property
If you have a gas boiler then it won’t be able to ignite without a gas supply. Check another appliance in your home that runs on gas such as a hob to ensure that the gas supply to your property has not been interrupted.

If you have no gas supply then you will need to contact your utility company and tell them about your cold shower experience, they will no doubt make it their top priority to get it sorted.

For homes with a prepayment meter, ensure that you have enough credit.

Check the timer on your boiler
An easily overlooked issue is an out-of-sync timer or smart thermostat. If you use the timer on your boiler and there’s been a power cut in your area it can result in the timer getting out-of-sync and the heating won’t come on when you expect it to. Just check the dial on the boiler is set to the correct time.

Similarly, if you have a smart thermostat that loses connection to your internet, it could get out of sync, in the same way the timer on your boiler can. Just check the settings on your smart thermostat to ensure the timing is correct.

Crank the heating up
It’s worth turning your heating up above 21 degrees Celcius to check your boiler is turned on, if the room temperature is below this then your boiler may be off because it isn’t cold enough for it to switch on. Turn your thermostat up and see if it kicks in.

Check your fuse box
The final basic check to rule out is a tripped fuse in your fuse box. Your boiler won’t ignite if it has no power supply. If any fuses have tripped turn them back on and try again.

If your boiler is flashing an error message at you then you know it has power, if the LCD screen is blank then there is a good chance it has no power.

Once you’ve established your boiler has a fuel and power supply we can look at some more likely candidates as to why your boiler won’t turn on.

Low water pressure

One of the more common reasons for your boiler locking out and not igniting is due to low water pressure. This is often caused by a small leak in your system, like a drip on a radiator, which over time will decrease your system pressure until it causes a lockout.

The ideal pressure level is between 1 – 1.5 bar (the green section on the pressure gauge on your boiler).

If you’ve recently had a boiler installed or recently bled your radiators then there is a good chance that you’ve released air from your system causing the pressure to drop.

We’ve already covered why your boiler is losing pressure in a previous article, which explains the potential causes for why your boiler might be losing pressure and detailed instructions on how to repressurise your boiler.

The good news is, that this is one you can fix yourself in just a few minutes without any technical know-how.

If there is a leak coming from your boiler or the pipes beneath the boiler then you will need a Gas Safe Engineer to take a look as there is a malfunctioning part. If the leak is coming from a radiator or radiator valve then you can repressurise the boiler but you will need to fix the leak or the system will continue to lose pressure.

Every boiler is different, so we recommend referring to your boiler manual if you have it, or searching for it online if you don’t. Some boilers have filling loops and some have internal filling keys, it’s the same principle to repressurise but slightly different methods are used.

  • Switch off your boiler and let it cool completely
  • Find the filling loop (flexible silver cable) and make sure both ends are tight or you may have an internal filling key but it’s the same principle.
  • Open bath valves or turn your internal filling key to allow cold water into the system, this will repressurise the system.
  • When the gauge reaches 1.5 bar close both valves.
  • Remove the filling loop if it isn’t a permanent attachment.
  • Turn the boiler back on.

Once you’ve completed the steps above and the pressure has been increased, your boiler should now fire up and provide you with the warmth you deserve.

Frozen condensate pipe

We’ve covered ‘How to unfreeze a condensate pipe’ in a previous article but for those of you that somehow managed to miss that absolute gem we’ll cover the basics again.

Condensing boilers (any boiler installed after 2005) have a white plastic pipe coming out of them (you guessed it, the condensate pipe) which transports waste acidic water from your boiler outdoors to either a drain or a waste pipe.

In particularly cold weather, the water in this pipe can freeze. This will cause a backing up in the system as the water has no way out. The system will then lockout to prevent any harm from coming to the boiler.

Your boiler will then display an error code to inform you that you have a frozen condensate pipe. You may also hear a strange gurgling noise coming from your boiler.

This is another issue you can easily fix yourself by pouring some warm water on the frozen area of the pipe to melt the frozen water inside.

If you think you may have a frozen condensate pipe then we recommend reading our article on how to fix a frozen condensate pipe as it goes into the issues, fixes, and prevention in a lot more detail.

Gas valve fault

The gas valve in your boiler is responsible for controlling the flow of gas into your boiler. If you request a higher temperature, the gas valve will open and allow more gas into the boiler to be burned to heat your home.

If there is too much or too little gas being supplied your boiler will lockout for safety reasons. You should not attempt to resolve any issue linked to a gas valve yourself, you will need to call a Gas Safe engineer.

Gas valve issues can arise due to a blockage stopping the gas flowing or from a wiring malfunction. Usually, it’s an issue with the adjustment of the gas valve and it’s not a major job to fix and will cost in the region of £220.

If you have a boiler that is already over 7 years old and you’ve previously had issues with it then rather than continuing to sink money into it, it might be worth getting an instant quote from WarmZilla on a new boiler.

Gas pressure

We’ve already done a basic check to make sure your property has a gas supply coming into the property but your boiler will also lockout if the gas pressure is either too high or too low. A Gas Safe engineer will need to test your gas supply to ensure you have the correct gas pressure.

In particularly cold weather the regulator on gas meters can freeze and this will affect your gas supply. This issue can be resolved by lagging your gas meter box.

Faulty ignition lead

If, when trying to ignite your boiler you can hear a clicking noise then you may have a faulty ignition lead or electrode. This is the part responsible for providing the spark that fires up your boiler.

This is something a trained engineer will need to take a look at. They will check the electrode and ignition lead with a multimeter to see if there are any issues. If there is a fault with your ignition lead then it will cost around £200 to fix.

Fan malfunction

The fan within your boiler creates a draught that draws the harmful gases produced as a by-product of burning gas out through the flue in your boiler.

If there is a malfunction with the fan then your boiler will lockout as a safety precaution. You will need to call a Gas Safe engineer to look at your boiler.

If there is an issue with the fan on your boiler then you can expect to pay between £200 – £275, depending on the heating engineer and the area of the country you live in.

Pilot light has gone out

On older boilers, particularly back boilers, the pilot light might have gone out. You can try to relight the pilot light yourself but if the pilot keeps going out then there is likely an issue that will need to be looked at.

The jet for the pilot light has a very small aperture at the end, which can easily become blocked and require cleaning out. Again, you can do this yourself but we would recommend getting a Gas Safe engineer out just to check that everything is in good order.

If you have an issue with a back boiler then we would recommend not spending any more on it. They are old, inefficient, and bad for the environment. Replacing an old G-rated boiler for a modern A-rated boiler can save you up to £315 per year on heating bills.

Other possible causes

There are a number of issues that could cause your boiler to fail to ignite. Above we have looked at the most common causes as to why your boiler might not switch on.

If you have gone through the issues above and ruled them out then it might be time to call in a professional and get them to check over your boiler. You shouldn’t take any chances when it comes to gas boilers, it’s illegal for anyone other than a Gas Safe registered engineer to work on a boiler.

To help you identify the issue with your boiler you will often be given an error code that you can look up in the boiler manual or on a helpful WarmZilla blog to see exactly what is causing the issue with your boiler.

Click on any of the boiler brands below to be taken to the boiler error code page for that brand:
Viessmann Boiler Error Codes / Fault Codes List
Ideal Boiler Error Codes / Fault Codes List
Worcester Boiler Error Codes / Fault Codes List
Vaillant Boiler Error Codes / Fault Codes List

If you still don’t have an answer to your question after reading this blog then please use our live chat to ask us anything, we’re always happy to help if we can.

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