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Trusted by over 500,000 customers for 20+ years
Order online or call
01480 775454
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Trusted by over 500,000 customers for 20+ years
Written by
Camilla George
on 31 Mar 2026
and updated on
31 Mar 2026
Categorised in
Tips and Advice
A working oil boiler is essential for keeping your home warm, especially during colder months. If your oil boiler is not working, the cause is often one of a few common issues that can be identified quickly.
In this guide, we explain the most common reasons an oil boiler breaks down, how to spot the signs, and what you can do to fix the problem safely.
If you are ever unsure, it's always best to contact a qualified OFTEC engineer.
If your boiler has stopped working, it will usually be due to a disruption in fuel supply, system pressure, or pipework. In many cases, the boiler will enter a safety shutdown (known as lockout) to prevent damage.
The most common causes are running out of oil, incorrect boiler pressure, or a blocked condensate pipe. Less commonly, issues such as clogged filters, ignition faults, or thermostat problems may also prevent the boiler from firing.
Before calling an engineer, it's worth checking a few of these common issues first.
There are often warning signs before a complete boiler breakdown. You may notice that your boiler is not firing up, your heating or hot water has stopped, or the system keeps locking out.
Some boilers will display an error code, while others may make unusual noises or show a drop in pressure. Recognising these signs early can help you identify the problem more quickly.
Running out of oil is the most common reason an oil boiler stops working. Without fuel, the burner cannot ignite, and the system will shut down.
This should also be your first check. If your tank is empty or low, arranging a delivery and topping up will usually resolve the issue. Once refilled, you may need to reset the boiler to restore normal operation.
If your boiler pressure is too high or too low, the system may shut down for safety reasons.
High pressure is usually caused by too much water in the system and can often be reduced by bleeding your radiators. Low pressure, on the other hand, may indicate a lack of water or a potential leak. If no leaks are visible, you can increase the pressure using the filling loop.
Your boiler manual will show the correct pressure range, which is important to maintain for safe and efficient boiler operation.
During colder weather, the condensate pipe can freeze or become blocked, preventing your boiler from working.
This pipe removes wastewater from the system, and if it's obstructed, the boiler may shut down. To fix this, you can carefully pour warm (not boiling) water over the pipe to thaw it. Once cleared, resetting the boiler should get it running again.
If this happens frequently, insulating the pipe can help prevent future problems.
Regular maintenance is the best way to avoid unexpected boiler issues. An annual service by a qualified OFTEC engineer ensures that your system is running safely and efficiently.
It's also important to keep your oil tank topped up, check your boiler pressure occasionally, and protect external pipes during cold weather. These simple steps can help reduce the risk of breakdowns and extend the life of your boiler.
While some boiler issues can be resolved with basic checks, others require professional attention. If your boiler continues to lock out, fails to ignite, or shows signs of a more serious fault, it's best to contact a qualified OFTEC engineer.
You should also avoid attempting repairs involving internal components, oil lines, or electrical systems unless you are properly qualified.
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