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Boiler Not Firing Up? 7 Reasons and Instant Fixes

Central heating and hot water are two of life’s essentials. So, there’s nothing worse than waking up to discover your radiators are off, the shower is cold and your boiler isn’t firing up. Your first reaction may be to call a heating engineer, but before you do that there are some simple at-home fixes you can try that may just save you time and money. Read on to find out the causes behind your boiler not firing, as well as the solutions to fix it!

Why is My Boiler Not Firing Up?

1. Power Failure

Your boiler will use a small amount of electricity to fire up and will therefore fail to work if there’s a lack of power. Reasons for no power include:

  • A power outage
  • A manual change being made to the thermostat settings
  • The boiler accidentally being turned off
  • The circuit being overloaded, causing the fuse to trip

To know if your boiler fuse is blown, check your home’s fuse box to check whether the circuit is off. You’ll know this because the switch will be pointing down, and so to resolve this, simply flick the switch back up.

When there’s an ignition fault on your boiler because of a power failure, it can cause a lockout. This is an in-built feature designed to shut the boiler down and prevent damage when a fault occurs. Some models will display an error code when this occurs. Common codes you may see include:

Boiler Brand Boiler Codes/Lights
Baxi · E317
· E13
Glow-Worm · Green LED off
· F17
· F76
· F83
Ideal · L2
Vokera · Red light flashing
· Red light constantly on
Worcester · FD 231
· C1 64
· Thermal fuse lockout


  • Activate the boiler’s reset button. Press and hold for 10 seconds. Wait for the boiler to restart by igniting. Usual signs that this has worked include a green indicator light being on or any previous error codes disappearing.
  • If the fuse has tripped, flick the switch back on.
  • Ensure the isolation switch next to the boiler is on.

2. Trapped Air

If your radiators have cold spots at the top, it can be a sign of trapped air. Central heating works to warm up your home by circulating hot air through the pipe and into the radiators. Over time, however, pockets of air can form which rise to the top whilst the hot water stays at the bottom, hence the radiator tops being cold. This, in turn, can lead to your boiler not firing correctly.

Error codes you might see include:

Boiler Brand Boiler Codes/Lights
Baxi · 110
· E1
· E2
· E4
Glow-Worm · F32
· Boiler locks out
Ideal · Overheat lockout
· Water pressure
Vokera · A01
· 10
Worcester · A1 281


  • Perform a radiator bleed to release trapped air. This is a relatively simple DIY job but if you don’t feel comfortable, then a heating engineer can easily do this for you.

3. Frozen Condensate Pipe

The condensate pipe is a plastic pipe that drains away acidic wastewater from the boiler, and whilst it can sometimes be found inside, it is more commonly placed outside which makes it susceptible to freezing in colder temperatures.

If it freezes, the sensors on your boiler will detect this meaning your boiler won’t turn on. There will be no flame on the boiler as the sensors stop it from working to protect the system. If you suspect your pipe has frozen, then you may be able to hear gurgling sounds. An error code would, of course, also let you know. 

Error codes include:

Boiler Brand Boiler Codes/Lights
Baxi · E133
· E28
Glow-Worm · F1
· F29
· F4
· F28
Ideal · Boiler fires up for a short time, then turns off
Vokera · 92
· 93
· 95
Worcester · EA 229
· D5


  • Perform a radiator bleed to release trapped air. This is a relatively simple DIY job but if you don’t feel comfortable, then a heating engineer can easily do this for you.

4. Faulty Diverter Valve

The diverter valve directs the hot water flow to the taps or heating within your home. If you have heating but your boiler isn’t firing up for hot water – or the boiler is clicking but not igniting – then it’s likely that you have a faulty diverter valve. It’s a common “wear and tear” issue that causes the valve to stick.

Error codes include:

Boiler Brand Boiler Codes/Lights
Baxi · H.01-.00
· E.02-.17
· E.04-.17
· E09
· E15
· E134
Glow-Worm · F26/F77
· F14
· F.61
· F.82
Ideal · FU
Vokera · 10
· A01
Worcester · FA
· FA 364
· FB 365
· F0 238
· EA 234


  • This isn’t a DIY fix sadly so you will need to call out a Gas Safe engineer who will look to either clean, replace or release the diverter valve. It may be worth having the engineer take a look at the overall health of your boiler as, with older models with other underlying issues, it might be more cost-effective to simply replace the boiler.



If you’ve recently had a power cut, then it could have affected the timer. This means that it doesn’t fire up at the time you’d previously set it to, and has reverted to factory settings.

You may also have issues with your thermostat whereby it’s misreading the temperature causing ignition issues. If your thermostat is set too low or located near a source of heat, then your boiler will not ignite as the room temperature is higher than that set on the thermostat.

Error codes include:

Boiler Brand Boiler Codes/Lights
Baxi · E110
· E20
· E.04-.08
· E20
· E28
· E40
· E50
· E110
· E130
· E163
Glow-Worm · F85
· F00
Ideal Turn your thermostat to maximum and check if a C comes on. If it does, then the thermostat wasn’t set high enough. If it still doesn’t fire, then contact a heating engineer
Vokera · A02
· A77
· E020
· E077
Worcester · E9 224


  • Check that the time on the boiler is correct
  • Reset the timer. If you do this, the timer will reset to factory settings so make sure that you change to the correct time after performing the reset.
  • Turn up the thermostat to max and check if the boiler fires up.
  • Change the location of your thermostat if it’s near a source of heat such as a radiator or oven.
  • Check that the heating hasn’t been turned down.

6. No Gas Supply

Another major cause behind your boiler not firing up is an interruption to your gas supply. If the supply to your home is interrupted, then there’s little you can do about it yourself. Another issue that would affect the pressure, meaning your boiler won’t ignite, is if your gas meter is frozen. This would also cause an insufficient gas supply to your boiler.

It’s also worth checking the gas valve, which stays open to provide fuel, as if this is damaged then gas is unable to enter, therefore this could be another reason why your boiler isn’t firing up.

Error codes include:

Boiler Brand Boiler Codes/Lights/Faults
Baxi · E133
Glow-Worm · F14
Ideal · F2
Vokera · 1
· AL40
· AL41
Worcester · EA


  • Ensure your gas supply is still switched on.
  • Contact your gas supplier to see if there are any issues locally or whether there’s an outstanding, unpaid bill.
  • Insulate your gas meter to prevent it from freezing in the colder months. Try lagging your meter by adding insulation.
  • If you’ve recently updated to a high-efficiency combi boiler that isn’t firing up for hot water or central heating, then the issue could lie with your gas supplier as your current gas supply might be too old for the new technology. A Gas Safe plumber can test the gas pressure outlet and confirm if it’s too low. If this is the case, then contact your energy supplier as soon as you’re able.

7. Pressure

When a boiler is lacking pressure, it will be unable to fire up. Normally, the water pressure on your boiler’s gauge should be set at around 1-2, although it’s always best to check the manual for your specific model’s pressure levels.

Boilers will lose pressure over time, but if there’s a sudden drop then it’s likely that there is a leak. Pressure loss can also occur if you have recently carried out a radiator bleed. If the pressure rises above 2, then the pressure valve may have loosened, or your radiators may need bleeding.

Error codes include:

Boiler Brand Boiler Codes/Lights
Baxi · E117
· E78
Glow-Worm · F32
· F73/F74
· F9
· F09
· F.22
· F.75
· F.72
Ideal · F1
Vokera · A04
· AL41
· AL40
Worcester · CE 207
· H07


  • If your boiler pressure is too high, bleed the radiators.
  • If your boiler pressure is too low, repressurise the boiler.

Frequently Asked Questions (FAQs)

“Why is there no pilot light on my boiler?”

The pilot light is an essential part of your boiler that works to ignite the gas supplied to the boiler to heat your home and give you hot water. There are a number of reasons that your pilot light has gone out. The most likely reasons are as follows:

  • A faulty thermocouple
  • The pilot orifice needs cleaning
  • Misfiring gas regulator
  • A draught

Whilst you can relight the pilot light by yourself, if you suspect that you have a broken thermocouple, then it’s important that you contact a heating engineer. Gas does still flow when the pilot light goes out which is dangerous. As such, any DIY job performed on this could lead to further damage, or even carbon monoxide poisoning, which is fatal.

“The pilot light on my boiler is on but it isn’t firing up. Why is this?”

If your boiler won’t fire up but the pilot light is on, then it’s likely that there’s one of the following issues:

  • Insufficient pressure
  • A blockage in the burner
  • Frozen condensate pipe
  • Frozen gas meter
  • Faulty diverter valve

“What do you do when your boiler won’t turn on?”

If your boiler won’t turn on, then first, check to see if other electrical items are working in the home to ensure there hasn’t been a power outage. If they are working, then check the fuse box to see if the boiler has tripped. As always, if you’re unsure of the cause, contact your local heating engineer. It’s always better to be safe when it comes to boiler functioning.

“Why is my boiler on but I have no heating?”

If you find that you have no heating, but your boiler is working, then it is likely you have an issue with: your boiler pump, the thermostat or the timer. If you have cold radiators, then check that the thermostat and timer are functioning correctly.

“Should I turn my boiler off if it has a fault?”

If you suspect your boiler has a leak, then you should immediately turn it off. Turning your boiler off, if there is a fault, will do no harm, and you shouldn’t leave your boiler on continuously, but you should seek advice from a heating engineer as prolonged periods of downtime time can have an adverse effect.


Many boiler issues can be solved by performing a system reset with instructions found in your boiler manual. If you suspect a fault but don’t feel confident fixing it yourself, contact a heating engineer to resolve the issues.