Boiler Not Working? Common Problems, Fixes & Costs

A broken down boiler might make you want to immediately phone an engineer.

Below, we’ve given a guide on diagnosing what’s wrong, including:

• 6 steps for checking your boiler (without any assistance)
• 6 common boiler problems (& their repair costs).

So, read on to see if you can solve your broken boiler’s problem.

Important note: Boiler repairs can be hazardous. This guide helps identify issues, but you should always consult a Gas Safe registered engineer to ensure your home’s safety and maintain your manufacturer’s warranty.

6 steps for checking your boiler

1. Run through the basics

If you use a prepayment meter, check that you haven’t run out of credit. 

(Some will offer a small amount of emergency credit, so make sure you haven’t run your meter into negative credit.)

You should also check your gas supply. Turn on another gas appliance, like a gas hob, to see if it’s working. 

Finally, check if your fuse box has tripped.

2. Have you had a power cut lately?

Interruptions to power supplies can reset boilers’ timer settings.

This will mean that your boiler won’t turn on and off at the right times. Check the time on the boiler controls to see if it is correct.

You may simply need to reprogramme your boiler controls with the correct date and time.

3. Check the boiler pressure gauge

If your boiler’s pressure gauge is showing a pressure of below 1 bar, the pressure might be too low for your boiler to function correctly. 

In some cases, homeowners can repressurise boilers themselves. However, if you aren’t confident in your ability to do this, call an engineer.  

4. Turn up your thermostat

Check your thermostat is set higher than the current room temperature. 

Boilers only fire when there's a call for heat. This means that the thermostat's target temperature needs to be above what the room is actually measuring. 

If in doubt, turn it up to 21°C and see if the boiler responds.

5. Reset your boiler 

Check your boiler’s instructions to see if there is a reset function. If there is, reset and see if this problem is still present.

6. Check the pilot light

If your boiler was installed before 2005, it will likely have a pilot light. 

Check that the pilot light is on. If it isn’t, then you may be able to relight this yourself. Check your boiler’s instruction manual to see if and how you can do this.

6 common boiler problems (& their repair costs)

1. Heating pumps

Your heating pump is the heart of your system. It takes hot water from your boiler and pumps it around your pipework. 

So, if it stops, you may experience several problems, including:

• Radiators suddenly stopping working
• Boiler becoming noisy 
• A leak from below your boiler. 

Many things can cause a pump failure, from the propeller on the pump getting stuck to air building up in the pump and causing an air lock. 

Cost to fix  

It’s likely to cost around £200 for a replacement pump, plus the cost of a boiler repair engineer to fit it.

2. Faulty circuit board

A circuit board developing a fault may cause you boiler to do any of the following:

• Losing power
• Working sporadically 
• Show flickering on its display panel.

The loss of your boiler’s power could also be caused by a blown fuse in the boiler, so make sure you check this first. 

But if the fuses are all fine, you’ll probably need a replacement circuit board.

Your circuit board failure could be caused by many things. A leak in the boiler or the circuit board developing a crack are amongst the most common.

Cost to fix

Depending on the type of boiler you have, a replacement circuit board is likely to cost up to £250, plus the cost of a boiler repair engineer to fit it.

3. Broken thermocouple

A thermocouple is a device that decides whether a pilot light is lit. If there is a problem with it, your boiler won’t turn on for safety reasons (i.e. to stop excess gas being released).

In this event, you might also notice your pilot light not working.

Your broken thermocouple is likely to be caused by metal fatigue. This will be largely due to its age and the changes in temperature it’s been exposed to over time. 

The continuous expansion and contraction of the metal causes the thermocouple to become weak and potentially fail.

Cost to fix

Replacement thermocouples parts are inexpensive. But the cost for a boiler engineer to fit it is likely to be approximately £150. 

4. Broken pump seal

Dripping or a leak from underneath your boiler is often a sign your pump seal or pressure valve has broken inside your boiler. 

A broken pump seal is usually caused by the age of the part. Over time, it wears down and will need to be replaced.

Cost to fix

Your boiler repair engineer will probably advise you to have the whole pump replaced, rather than just the seal. 

If your pump is old, it’s likely to break down soon anyway. Expect to pay approximately £300 for the replacement pump and the engineer’s labour.  

5. Faulty boiler fan

Do you have an air fault code showing on your boiler? If so, it’s likely that your boiler’s fan has developed a fault. 

The place to check is your boiler’s display screen.

Your boiler’s fan is a critical component. It pushes harmful gases through your boiler’s flue and out of your home.

If your fan can’t do its job, your boiler’s circuit board won’t allow the boiler to turn on.

Your fan’s fault has probably been caused by the windings on the motor getting burnt out or the bearings having deteriorated.

Cost to fix

The cost of a replacement fan will vary, depending on the model of your boiler. 

But you can expect to pay between £100 and £200 for the fan, plus approximately the same again for a boiler repair engineer to fit it.

6. Motorised valve failure

Are your radiators not heating up? Have you found yourself with no hot water? 

If so, it’s possible your boiler’s motorised valves have failed. Your lack of hot water and heating could, of course, be caused by other problems with your boiler, including a drop in your boiler’s pressure. 

So, before you call out an engineer, it’s always a good idea to check your boiler’s pressure is between 1 and 1.5 bars on the pressure gauge.

Like any moving part, the motorised valve in your boiler is subject to wear and tear.

Replacing the motorised valve is a major job, as your heating system will need to be drained to remove and replace the part within the boiler.

Cost to fix

Expect to pay approximately £300 for your replacement motorised valve and for the boiler repair engineer to fit it.

The importance of services

A regular boiler service is one of the best ways to reduce the chance of breakdowns, which you can get free with our home boiler cover. 

With our emergency cover, you could also call out an engineer to check and fix your boiler if none of the above steps got things back up and running.

Autumn boiler problems

Did you know your boiler is most likely to have a problem during the Autumn? 

This is due to your central heating system being inactive during the summer months. But whenever a boiler failure occurs, it’s never ideal and always inconvenient. 

Consider boiler cover 

Common boiler problems and repair costs are both inconvenient and expensive. So, want to know you’re protected against these unexpected expenses?

With boiler cover plans starting from as little as £11 per month, YourRepair gives you access to:

• Over 5,000 gas safe engineers across the UK
• A UK-based call centre open 24 hours a day 
• An annual boiler service and safety check included.

For instant protection, call our friendly team on 0330 029 3348 and never worry about common boiler problems and repair costs again.