Common issues and simple fixes for when your boiler isn’t firing up

Here at Swale Heating we understand that waking up to discover your boiler isn’t firing up and you have no heating and hot water is not a great start to the day. We are on hand 24/7 with Gas Safe certified engineers to help with your boiler repairs.

However, sometimes there are a few simple checks you can do at home to save you some time and money. We have put together a few steps below for you to follow to help you understand the issue and get your boiler up and running as soon as possible.

Power failure

Boilers use a small amount of electricity to fire up, if there is a lack of power the boiler will be unable to do so. There are a few reasons why there could be no power:

  • Power cut or outage - are other electrical appliances working?
  • A manual change was made to the settings on the thermostat.
  • Could the boiler have been accidentally turned off?
  • There could be a circuit overload causing the fuse to trip.

A power cut is easy to diagnose, check your other electrical appliances to determine if the power is out in your whole property. Power cuts often happen when there have been extreme weather conditions like snow, wind, and rain.

Tripped fuse

F­­irstly, check your home’s fuse box to see if the circuit is off. The switches will be pointing down - you can resolve this by flipping them back up. When a fault like this occurs, it will cause the power to your boiler to stop for safety reasons and to prevent damage to the boiler. Ensure you check the isolation switch next to your boiler is on. Once your boiler turns on it may show an error code, your boiler manual will have a breakdown of each code to help you work out how to reset your boiler and get it back up and running.


Power cuts can also affect the thermostat or timer. It may have been reset to factory settings meaning any timers for the boiler to fire up at specific times may have been removed.

Thermostats can also misread temperatures if they are in areas where the temperature is too high or low, this will affect when and if the boiler will fire up.

You should also check that the time on the thermostat is correct, reset the thermostat/timer back to factory settings and re-input your chosen times and schedule. Try moving your thermostat to another area in the home if you think this could be causing the boiler to misread the temperature.

Trapped air

If your radiators are on but have cold spots at the top, or if the heat is not evenly distributed across the whole radiator you may have air trapped in the system. This can cause the boiler to not fire up and sometimes can result in an error code displaying on the boiler.

Use your boiler’s manual to identify the boiler code, this will help you reset your boiler; however you may still need to bleed your radiators to release the trapped air. This is an easy process that you can perform at home with a radiator key, and a rag to soak up the water, use our ‘how to bleed a radiator’ guide to help you through the process.

If you don’t feel comfortable doing so and are an existing Swale Heating customer, you can sign in and book an appointment using our online portal.

You may require a more in-depth cleaning of your central heating system if the issue persists after you have bled your radiators. We offer a range of central heating cleaning services request a free, no-obligation quote online using our contact form.

Frozen condensate pipe

The condensate pipe is a plastic pipe that drains away acidic wastewater from the boiler. The condensate is located outside which in colder months means it is susceptible to freezing.

There are sensors on the boiler to protect it and they will stop the boiler from firing up if it detects the condensate pipe is frozen. Alike the other potential problems mentioned, your boiler will likely show a fault code. You may also hear gurgling sounds which is also an indicator your condensate pipe is frozen. Use our ‘guides to frozen pipes’ to find our more information.

Faulty diverter valve

A diverter valve is used to direct hot water flow to the taps or heating in your home. If you have heating but the hot water doesn’t seem to be working, then you may have a faulty diverter valve.

Another sign of a faulty diverter valve is clicking when trying to ignite the boiler. Unfortunately, this can happen with general wear and tear and happens when the valve sticks.

This isn’t a simple fix and will require the expertise of a Gas Safe engineer, book an appointment online and one of our team will endeavour to help and get someone out to you without delay to clean, replace or release the faulty diverter valve.

Boiler pressure

A lack of pressure will prevent your boiler from firing up, the water pressure on the boiler’s gauge should be set at around 1-2, although it is best to check your boiler’s manual for accurate model pressure settings.

Boilers can lose pressure over time however, if there is a sudden drop in pressure that could indicate a leak. Boiler leaks can be dangerous, if you’d like more information about boiler leaks and what can cause them, give our ‘Is your boiler leaking water, here’s what to do’ guide a read.

Boiler pressure may also drop after a radiator bleed so it’s best to check this after you have bled your radiators and adjust accordingly. If the pressure has risen this can be a sign that the pressure valve is loose or that the radiators need bleeding.

No pilot light

A common reason for a boiler not firing up is that there is no pilot light. Pilot lights go out when there is a blocked jet, they can become easily blocked by small amounts of debris. If you suspect your pilot light needs replacing, book an appointment online and one of our team will endeavour to help and get someone out to you without delay.

Attempting to repair a boiler can be extremely dangerous, additionally, if a boiler is repaired incorrectly the issue could worsen and lead to more serious problems. Please do not try to perform any repairs that require a Gas Safe engineer.

Here at Swale Heating, all our Gas Safe certified engineers are experts in central heating repair and use genuine boiler parts from trusted brands. For any boiler repairs please visit our boiler repair page for further information.