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Boiler not firing up how to fix

Boiler losing pressure

Why is my boiler not firing up?

You’ve just got home on a cold winter evening, and you’re looking forward to stepping into your cosy home and having a long soak in the bath. So, when you’re met with a freezing cold house and no hot water, getting the boiler up and running as quickly as possible is going to be your top priority.

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But if you try and get it working and you’re still left with the boiler not firing up, we have some help and advice for you.

Thankfully there are some boiler problems that you can check for that might mean the boiler is up and running in no time. And if they don’t resolve the issue, then there are also some really easy DIY solutions that you can try before you reach for the hot water bottle!

If you do need to call out an engineer, remember that for them to work on a gas appliance, they will need to be a gas safe registered engineer.

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Things to check first

So sometimes, it’s not the boiler itself that’s the cause of the problem. These are the things to check first to see if you can quickly have your home nice and warm.

Thermostat setting

If your boiler thermostat is set to a low temperature, then it’s entirely possible that even though it feels cold that it’s not yet got cold enough to trigger the heating to come on. It can be really easy to knock the dial or accidentally drop the minimum temperature, so take a look at that first.


Next on the list is to check the boiler timer. Have you accidentally set the heating to come on later than you thought? Maybe you changed it last week when you were going to be home later and then forgot to change it back.

If the timer is set to come on after you arrive home, then that’s going to be the cause of the frosty reception. Another reason for timer issues can be if there’s been a power cut. That can then cause the timing to get out of sync.

Gas supply

Is the gas supply working? If you have other gas appliances such as a gas cooker, try that to see if that’s working okay. If gas appliances are limited to the boiler, then maybe nip round to a neighbour to see if their gas supply is working okay.

Sometimes the gas pressure coming to your home can cause problems. If there is low gas pressure, then the flow may not be enough for the boiler to ignite.

If there does seem to be a problem with the gas supply, and that’s either no supply or gas pressure problems, then you should call your gas supplier or the Gas Emergency Service on 0800 111 999.

Carbon monoxide

While we’re talking about the gas supply, if your boiler is lighting, but there’s an orange or yellow pilot light, then it could be producing carbon monoxide. This is one of the harmful gases that can be fatal.

If the pilot light on your boiler is anything other than a crisp blue, you should turn the boiler off and call a gas engineer to come out and inspect it for you.

Electricity supply

Even a gas boiler needs some electricity to ignite. It doesn’t need much, but if there’s no power supply, then it’s not going to turn on and that’s going to mean a lack of heating and hot water.

Fuse box

Next up is to check the fuse box. If there have been problems with the electricity supply then you might find that the fuse to the boiler needs resetting.

Prepayment gas meter

If you have a prepayment gas meter then do have a quick check to make sure that you have enough credit for the boiler to fire up.

Error codes

Although boilers are pretty straightforward there are a number of different problems that can occur. So most systems have a boiler display on which a fault code is shown. Then, when the boiler isn’t working in the way it should you’re provided with information on what the issue is.

Now, do bear in mind that each boiler brand uses different codes, so that means that Baxi boiler error codes for a pressure issue will be different from the error codes for Worcester Bosch boilers. There can also be some variations between the different models, even from the same manufacturer.

If you have your boiler handbook to hand that will list all the error codes along with their meaning. If you’re not sure where the handbook is, you’ll be able to download another copy from the website for your boiler brand.

Things to try

So, you’ve tried and checked all of our first lists, now we’re moving on to more simple diagnostic checks that might help you to get the heating system up and working.

Resetting the boiler

If the electricity supply has gone off during the day, it can sometimes cause a boiler lockout situation. Not until the boiler is unlocked will it start to function properly.

This is another situation where you need to check the error code being displayed on the control panel. This will confirm that the boiler is locked out, and then your manual will give step by step instructions on how to unlock the boiler.

Check the pressure gauge

Your boiler needs a delicate balance of air and water for it to function correctly. The boiler pressure relates to the pressure of the hot water that’s flowing through your heating system.

The ideal pressure for your boiler is 1.5 bar but your system is likely to operate just fine with a pressure of between 1 and 2 bar. The pressure gauge on the front of the boiler will give you a reading of what the pressure is right now.

Low pressure

If there is low pressure then the boiler will fail to ignite. While high pressure, so anything over 2 bar, may result in a lockdown situation.

It is normal for boiler pressure to fluctuate a little and for it to decrease over time. But, if there is a sudden drop in pressure then that’s going to need further investigation by a heating engineer as it may be due to a fault with a pressure valve.

High pressure

If the boiler pressure is too high, then some of the radiators within your central heating system may need bleeding.

Bleed the radiators

To reduce the pressure in the heating system will need you to bleed all the radiators. This lets excess trapped air escape and rebalances the air and water in the system.

For this, you’re going to need the radiator key, a cloth, and a small container to collect any water that leaks out.

1. With cold radiators, place the cloth below the radiator bleed valve to catch any leaking water

2. Then use the key to open the valve, which in turn releases the air trapped in the radiator

3. Close the valve back up

4. Now recheck the water pressure meter on the front of the boiler

5. If you’re in the green then fingers crossed the boiler will come to life.

Frozen condensate pipe

The condensate pipe travels from the boiler to an external drain to remove excess liquid from the boiler. If there has been very cold weather then the wastewater can freeze causing frozen pipes and a blockage. Because the boiler can no longer get rid of the waste then it goes into lockdown.

This is another issue that’s easy to fix without needing the help of a boiler engineer. All you need to do is to pour warm water over the external condensate pipe to thaw the blockage and then reset your boiler.

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Issues with the central heating system and boiler

So you’ve done all the checks but you’re still having problems with the boiler not firing up meaning no central heating or hot water.

Now we get to the list of problems that are going to need the assistance of a gas safe registered engineer. Do remember that UK legislation is in place to prevent anyone who is not a gas safe engineer from removing the casing of a gas boiler.

Gas is a very safe energy source when it’s maintained by a professional and qualified engineer. If you have a relatively new boiler then you might still have warranty cover in place. For older boilers, a boiler cover plan can be a great option to avoid big and unexpected repair bills.

No pilot light

The boiler pilot light is the flame inside of the boiler that catches with the gas that then enables the water to be heated. If there’s no pilot light then the boiler is not firing to then enable the heating process.

One of the common reasons for there is no pilot light is because the pilot light jet has become covered in debris. The blocked burner is then unable to light up.

In older boilers, you can usually see the light of the flame through a small window in the boiler casing. On newer models, there will be an error code displayed to let you know that there’s a pilot light problem.

Burner replacements are a quick and easy job for your gas safe registered engineer to fix so you should have central heating and hot water back up and running in no time.

Faulty burner

When the burner is working it produces CO2 as waste gas. Over time this then causes the burner to become clogged up and develop mechanical faults. As a result, the burner might sometimes work and other times refuse to ignite.

The burner within your boiler does age over time and with wear and tear replacing it might be the best option.

Low gas pressure

In some cases the supply of gas to the home is normal but the boiler is not firing because the gas valve is preventing enough gas from getting into the system.

When this happens, the boiler will go into lockout mode and then display a fault code. This is when you then need to get in touch with a gas safe registered engineer who can test the pressure of the gas and work out why there’s not enough reaching the boiler.

Two causes of this problem are a gas meter that’s become frozen and a faulty gas valve.

1. Faulty gas valve

This is a more common cause of the problem as the gas valve controls the amount of gas that is able to flow into the boiler. It opens and closes which lets in more fuel or less depending on whether you need more heat or less.

The valve may have become damaged or blocked or it may just need adjusting to allow more gas to flow through. It’s also possible that a fault in the wiring to the valve can cause problems for it to function correctly.

2. A frozen gas meter

If the weather has been very cold then it is possible that the gas meter becomes frozen. Ensuring that the meter is lagged will prevent any future issues.

Electrode and ignition lead faults

If you can hear clicking noises when your boiler is trying to ignite then it could be that it’s the electrode and ignition lead that could be causing the problem.

More often than not, gas-related issues result in intermittent operation, so the boiler ignites for a second and then goes off again. If it is a problem with the ignition lead and electrode, then the boiler won’t be able to ignite at all.

A heating engineer will be able to use a multimeter to check out the electrode and ignition lead and confirm if that’s the problem behind the lack of central heating and hot water.

Faulty thermocouple

The thermocouple is a safety device that turns off the gas supply when the pilot light goes off. Its heat sensor is connected to a solenoid and when the sensor is not heated by the boiler’s flame, then the solenoid closes the gas supply.

When a thermocouple becomes faulty, it prevents the flame from staying alight. Generally, a boiler thermocouple that has burned out or is no longer operating correctly, can be replaced relatively easily by a heating engineer.

Time for a new boiler?

When it feels as if you can no longer rely on your heating system, then the time may have come to start thinking about a new boiler installation. No longer will you need to dread the latest boiler repair bill or astronomic energy bills from your inefficient system.

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Getting a new boiler quote is a great way of seeing recommendations for systems to meet your heating needs. And with boiler installations available within a few days of placing the order, your home could soon be ready for whatever the British weather can throw at it!

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