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Ignition Fault on Boiler: Cause & How To Fix

If you’re sat shivering and wondering why won’t the boiler ignite then help is here.

Viessmann vitodens 050 boiler

Without a working ignition on your boiler, you’re not going to get hot water or heating to your home no matter the boiler brand that you have.

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If your boiler is not starting up and if your ignition is faulty, it’s an issue that you’re going to want to get fixed as soon as possible, and will need the services of a suitably qualified professional such as a Gas Safe registered heating engineer.

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Ignition faults on boiler & how to fix

In this guide, we’re going to look at what might be causing the ignition problem, as well providing some advice on things to check before you call out the heating engineer or get a quote for a new boiler.

Eight quick boiler ignition checks to carry out first

It might be tempting to get straight on the phone to the boiler engineer when your boiler isn’t working. But, first of all, check whether boiler error codes are being displayed on the boiler control panel.

These will tell you exactly what the problem is and whether you can fix it yourself or will need a call out to a Gas Safe registered heating engineer.

We’ve then identified eight reasons why your boiler won’t ignite that you should check first before calling out the engineer.

1. Thermostat


If your thermostat is set higher than the ambient temperature, then the boiler isn’t going to fire up.

So, the first check is to ensure that the thermostat is set up correctly. Many modern boilers are set up via a smartphone and so rely on an internet connection to action any changes made to the settings.

So, if your boiler won’t ignite, then first of all check the thermostat settings. A new thermostat isn’t expensive and it could be a quick way to help your boiler work again.

2. Timer

The next step is to check the timer. Now while this isn’t an issue for homes with combi boilers, if you have a regular or system boiler you’ll have times set for the hot water to be heated.

Be sure to look into the best combi boiler, to see what the best ones are and how they hold up against regular and system boilers.

Have the clocks gone forward recently? Or has there been a power cut? Both can be common reasons for the boiler not coming on when you expect it to.

3. Fuse box

Now you need to check the fuse box. It’s not unusual for heating systems to be on their own power circuit, so that means that you might have power in other parts of the home but not to the boiler.

If you find the switch is down then you can move it back to the on position to see if that cures the problem.

4. Gas supply

inside vitodens 111-w

The next thing to check is to make sure that you have a working domestic gas supply, without that the boiler can’t ignite.

Check another gas appliance such as the gas hob to see if they light. If they do, then it’s not a gas supply issue that’s causing the problem with the boiler.

If the other gas appliances also fault to ignite then you’ll need to speak with your gas supplier to see what’s happening.

You could also check whether your neighbours have any problems with their gas appliances to know if it’s the supply to your home that’s an issue or if it’s a wider problem.

Is there any chance that you’ve forgotten to pay the gas bill? That’s definitely going to cause a lack of gas!

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5. Prepayment gas meter

If you have one of the prepayment gas meters installed then take a quick check to ensure that you have some credit. Without a gas supply then your boiler isn’t going to be able to fire up your central heating system or provide hot water.

6. Electricity supply

inside worcester 4000

Even gas boilers need a small amount of electricity to work.

So, again, check other electrical appliances to ensure that you have a power supply to the boiler. And, don’t forget to check that the switch is in the one position!

7. Water supply

Without water to heat up then there’s nothing for the boiler to heat. That’s then going to cause a flame failure. This is another of those reasons for why your boiler isn’t working that comes down to the utility provider.

8. Now reset your boiler

The final thing to do, before calling out a gas safe registered engineer, is to try a reset of your boiler. If you’re not sure how to do this, have a look at your boiler manual for instructions.

Boiler water pressure can cause the boiler not to ignite

With all the basic checks carried out, now it’s time to focus more on the workings of the boiler itself. One of the most common problems with boilers relates to low water pressure and that can be either too high or too low.

pressure gauge

To know which one might be the problem, take a look at the pressure gauge that you’ll find on the boiler display. On most models, you’ll see a green and red dial.

The first red zone means that the boiler pressure is too low, while the second red zone means that the pressure is too high.

When the needle is in the green zone of the pressure gauge then the pressure is within the correct range for your boiler to work correctly.

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Fixing high water pressure

High water pressure may be caused by a fault within the boiler or it might be because too much water was added to the heating system. If you’ve recently added water then this can be sorted out by bleeding the radiators.

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Bleeding the radiators

  1. To bleed your radiators, first of all, make sure that the boiler is switched off and cooled down. This is to avoid being scalded by hot water .
  2. Arm yourself with a container to catch the water and a towel to catch any drips
  3. Push the radiator key into the valve which you’ll find at the top of the radiator and to one side.
  4. Insert the key and you’ll feel it lock together with the valve
  5. Now turn the valve anti clockwise just one quarter turn
  6. You’ll hear the hiss of the trapped air escaping and then the water will begin to come out
  7. Now go back to the boiler and check the boiler pressure reading
  8. Repeat until the boiler pressure is at the correct level.

Fixing low boiler pressure

Low boiler pressure is often caused by a leak. All boilers will lose a little pressure over time, but if you find the level keeps dropping, or there’s a sudden decline, then you need to check the heating system to work out where the leaks might be.

If there are no leaks, then the problem might sit with the pressure release valve.

prv valve

Adding water to the boiler

  1. First of all find the filling loop which will have two handles at right angles at either end of the loop. Most boilers have this in place permanently, but there are a few boilers where the loop needs to be attached.
  2. Turn the boiler off
  3. Now turn both handles to a the same direction as the pipe
  4. You’ll now hear the water flowing
  5. Keep watching the gauge and turn off the taps as soon as the correct pressure is reached
  6. Now turn the boiler back on.
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Cold weather problems stopping igniting

If the weather has turned really cold then there are three things to check –

Frozen condensate pipe

The condensate pipe travels from the boiler to the outside of your home. The pipe transports excess liquid from the condensation of potentially harmful gases away, so when it becomes frozen, your boiler will fail to ignite. That then means no heating and hot water.

Sorting out a frozen condensate pipe is a quick and easy job. Simply pour warm water over the condensate pipe to thaw out the blockage.

Frozen gas meter

frozen pipe melting

If your gas meter is in a very exposed location and the weather very cold, then there is the possibility of it becoming frozen.

This would then cause a boiler lockout which then causes it to refuse to ignite.

This needs a call to your gas safe registered engineer for advice on the next steps to take. Simply chipping away at the ice could cause further damage to the meter.

Frozen pipes

If you have one of the boiler types that has a cold water tank in the loft then there is the possibility of the water pipes becoming frozen.

This then brings the risk of a burst pipe. A slow de-thaw using a portable heater or hairdryer on low settings is the best option here.

Faulty gas valves mean no ignition

A problem with the gas valve is another of the many reasons why your boiler doesn’t ignite. The gas valve controls the flow of gas to both the pilot light and the burner.

When the gas valve is open the fuel is then available to ignite the boiler and deliver more heat.

When the valve is closed then it blocks the flow of more fuel through to the boiler.

Cause of a faulty gas valve

When a gas valve prevents the gas boiler from igniting then it might be because:

  • it has become stuck or has seized
  • it’s corroded or there is debris blocking the valve
  • there is damage to the wired connections
  • worn out over time and use

This is a job for a qualified heating engineer and that’s because the boiler cover needs to come off.

A Gas Safe engineer will then be able to correctly diagnose the problem, and then get it fixed for you.

Sometimes if you’re getting repeated problems then the best option is to take the plunge and get a new boiler. You might actually be surprised at a new boiler cost, especially when you get a fixed price quote.

Problems with the pilot light igniting

The pilot light is an essential requirement for your boiler to supply hot water to your central heating system or your taps. The pilot light is the small blue flame that then lights a larger flame which enables the heating of the hot water.

Do be aware that if the pilot is burning with an orange or yellow flame, then this might indicate a carbon monoxide leak. If this is the case then turn your boiler off and open the windows.

You then need to evacuate your home and call the gas emergency line on call the gas emergency number on 0800 111 999.

Blocked pilot light tube

For the pilot light to work, the jet it comes from needs to be clear of any debris. It really doesn’t take much dirt for the pilot light jet to become blocked, so if that’s the problem then it needs to be cleaned.

If, however, you’re still having problems with the boiler not firing up then it will need to be replaced. When the gas injector tube is fitted incorrectly, it can lead to gas leaks. That means that this is a job for a Gas Safe registered engineer.

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Low gas pressure

If the mains supply is delivering a low gas pressure, then that can stop your boiler from igniting. This is another one to check whether people living nearby are having similar problems.

You’ll then need to report the gas pressure issues to your energy provider to resolve before you’ll be able to get your central heating and hot water back.

Ignition lead fault

The ignition lead is responsible for carrying the electrical supply to enable the pilot light to ignite.

A faulty ignition lead is going to mean that you’re going to get boiler ignition failure.

This will need a call out to your boiler manufacturer if your system is still under warranty or getting in touch with a gas safe registered engineer if you don’t have cover in place.

Ignition & Burner problems

For your boil to produce warm water or power your central heating, the boiler burns gases.

That, in turn, produces CO2, which can cause the burner to develop a carbon build up and that can stop it from working.

With the burner not working, the inevitable result is going to be the boiler not firing up.

There can also be issues with poor burner pressure, which is also caused by a carbon build-up. Cleaning the burner should be part of the annual service, so make you get this scheduled every twelve months to prevent problems.

Ignition broken? Time for a new gas boiler?

If you find yourself reaching for the hot water bottle because of a broken boiler then the time might have come for a new boiler.

No matter which boiler brand you have, older boilers will break down more often and it can be expensive to replace faulty electrical components.

Then there can also be declining levels of efficiency, and that means higher energy bills.

New boilers give you that confidence that you’ll come home to working central heating and a hot shower! So, the next step is to get a new boiler quote.

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