Posted on: 30 September 2026
You’ve turned the heating on, but nothing’s happening. Or perhaps you’ve gone to run the hot water and discovered your boiler isn’t playing ball.
Before calling an engineer, there are a few simple checks you can safely carry out yourself. Sometimes the problem can be as straightforward as a thermostat setting, low boiler pressure or an error that can be resolved by following the manufacturer’s instructions.
Here are 7 things to check if your boiler isn’t working – and how to know when it’s time to call in a professional.
1. Check Your Thermostat
Start with one of the simplest possibilities: your thermostat.
If the thermostat isn’t asking the boiler for heat, your boiler may appear to be doing nothing even though there isn’t actually a fault with the appliance.
Check:
- Is the thermostat switched on?
- Is it set to heating mode?
- Is the temperature set higher than the current room temperature?
- Is the timer or programme correct?
- If it’s wireless, do the batteries need replaced?
If you’ve recently started using your heating again after the summer, it’s also worth checking that your heating schedule hasn’t been changed or switched off.
Try increasing the thermostat temperature temporarily and see whether the boiler responds.
2. Look for an Error Code
Modern boilers will often display an error or fault code when something prevents them from operating normally.
Take a look at the boiler display for any letters, numbers, flashing lights or warning symbols.
If you see an error code, check your boiler manufacturer’s instructions to find out what it means.
Some faults may have a straightforward explanation, while others will require an engineer.
Don’t remove the boiler casing or attempt to investigate internal components yourself.
Make a note of the error code before contacting an engineer – it can be useful information when diagnosing the problem.
3. Check Your Boiler Pressure
Low boiler pressure is a common reason why some heating systems stop working correctly.
If your boiler has a pressure gauge or digital pressure reading, check whether it appears to be within the manufacturer’s recommended range.
The correct pressure can vary between boilers and systems, so always refer to the instructions for your particular appliance rather than relying on a universal figure.
If the pressure is too low, your boiler may display a fault or refuse to operate.
Some systems can be repressurised by the homeowner by following the manufacturer’s instructions. However, if you’re unsure how to do this, don’t attempt it.
It’s also worth paying attention to how often the pressure drops.
Having to repressurise the system once doesn’t necessarily indicate a serious problem. If your boiler is repeatedly losing pressure, however, there could be an underlying issue that needs investigating.
4. Check the Power Supply
It sounds obvious, but it’s worth checking that your boiler actually has power.
Look at the boiler display. If it’s completely blank, check whether:
- The boiler’s power switch is on
- A nearby fused spur has been switched off
- Other electrical appliances in the property are working
- A circuit has tripped
If a circuit repeatedly trips when the boiler is switched on, don’t continue resetting it. There may be an electrical fault that requires professional attention.
5. Check Your Gas or Oil Supply
Your boiler needs a fuel supply to operate, so check whether there could be an issue here.
Gas boilers
If you have other gas appliances, check whether they’re operating normally. If they aren’t, there may be an issue with the gas supply rather than the boiler itself.
If you smell gas, don’t attempt to troubleshoot the boiler. Follow the appropriate gas emergency advice immediately.
Oil boilers
If you have an oil heating system, check the level in your oil tank.
Running out of oil can prevent your boiler from operating and may require more than simply adding more fuel before the heating can restart.
If you use an electronic oil level monitor, remember that these can occasionally give inaccurate readings, so investigate further if the reading doesn’t seem right.
6. Can Your Boiler Be Reset?
Some boiler faults can be cleared using the boiler’s reset function.
However, resetting shouldn’t be used as a way of repeatedly overriding a fault.
If your boiler’s instructions recommend a reset for the error you’re seeing, follow the manufacturer’s procedure carefully.
If the boiler immediately locks out again or you find yourself regularly having to reset it, stop and contact an engineer.
Repeated lockouts usually mean there’s an underlying reason that needs to be identified.
7. Is It Actually the Boiler?
If your boiler appears to be running but part of your home isn’t heating properly, the problem might be elsewhere in the heating system.
Ask yourself:
- Are none of the radiators heating up?
- Are only one or two radiators affected?
- Do you have heating but no hot water?
- Do you have hot water but no heating?
- Are radiators cold at the top?
- Are some rooms taking much longer to warm up?
For example, a single cold radiator could point towards an issue with that radiator or its valve rather than a problem with the boiler itself.
Understanding exactly what’s working – and what isn’t – can also help your heating engineer diagnose the problem more quickly.
Boiler Still Not Working? When to Call an Engineer
If you’ve completed the simple checks above and your boiler still isn’t working, it’s time to get professional help.
You should also contact an engineer if you notice:
- Repeated boiler lockouts
- Pressure that continually drops
- Water leaking from the boiler or heating system
- Unusual banging, knocking or other persistent noises
- Error codes that keep returning
- Heating or hot water that repeatedly cuts out
- A boiler that won’t start despite the controls being set correctly
Don’t remove the boiler casing or attempt to repair internal components yourself.
Gas boiler work should be carried out by an appropriately qualified Gas Safe registered engineer like those at solv, while oil boiler work should be carried out by a suitably qualified Oftec technician. You can call us on 02890 451010 or book a repair on our website.
What If You Smell Gas?
A suspected gas leak is not a boiler troubleshooting job.
If you smell gas or suspect a gas leak, don’t use electrical switches or anything that could create a spark.
Open doors and windows where it is safe to do so, turn off the gas supply at the meter if you know how and it is safe, leave the property if necessary, and contact the Northern Ireland Gas Emergency Service on 0800 002 001.
Don’t wait for a routine boiler repair appointment.
Why Has My Boiler Suddenly Stopped Working?
There isn’t one single answer.
A boiler can stop working for a wide range of reasons, from a simple issue with the controls to a component fault that requires repair.
This is why looking at what changed immediately before the problem started can sometimes help.
For example:
- Has the heating only recently been switched back on after summer?
- Has the boiler pressure dropped?
- Has an error code appeared?
- Has there been a power cut?
- Has the thermostat stopped responding?
- Has the boiler been making unusual noises?
- Has the problem been getting progressively worse?
Make a note of anything unusual before speaking to your engineer.
Should I Repair or Replace My Boiler?
A boiler breakdown doesn’t automatically mean you need a new boiler.
Many faults can be repaired and, depending on the age and condition of the appliance, repair may be the most sensible option.
However, if your boiler is getting older, becoming unreliable or requiring increasingly frequent repairs, it may be worth discussing whether continued repairs or replacement makes more sense.
At solv, we provide boiler servicing and repairs as well as new boiler installations across Belfast and Northern Ireland.
If you’re considering replacement, you can also use our online boiler quotation tool to answer a few questions about your property and heating requirements and explore suitable options.
Don’t Ignore a Boiler Problem
If your boiler isn’t working, start with the basics.
Check the thermostat, look for an error code, check the pressure and make sure the boiler has power and an appropriate fuel supply.
You might discover a simple explanation.
But if your boiler keeps developing the same fault, repeatedly loses pressure, leaks, locks out or simply won’t start, don’t keep resetting it and hoping the problem will disappear.
Getting the underlying issue investigated can help get your heating and hot water back up and running – particularly as we head into the colder months.
Frequently Asked Questions
Why is my boiler not working but there is no error code?
Not every problem will generate an error code. Check the thermostat, heating programme, power supply and boiler pressure. If everything appears normal but the boiler still isn’t operating, contact a heating engineer.
Why is my boiler on but my heating isn’t working?
The issue could be with your thermostat, heating controls, valves, circulation or another part of the heating system rather than the boiler itself. Check whether all radiators are affected and whether you still have hot water.
Can I reset my boiler myself?
Many boilers have a reset function that homeowners can use by following the manufacturer’s instructions. However, if the boiler repeatedly needs resetting or immediately locks out again, contact an engineer rather than continuing to reset it.
Why does my boiler keep losing pressure?
Occasional pressure loss can occur, but repeatedly falling pressure can indicate an underlying problem such as a leak or an issue within the heating system. This should be investigated rather than continually topping the pressure up.
Who should repair a gas boiler?
Gas boiler work should be carried out by an appropriately qualified engineer who is on the Gas Safe Register.
Can solv repair my boiler?
solv provides boiler repair and servicing for homeowners in Belfast and the surrounding area. You can book a boiler repair online or contact the team if you’re unsure what type of appointment you need.