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Why is my radiator not working?

Looking to understand why your radiator is not working properly? Follow the steps below.

a bottom of a radiator with a TRV

What you'll learn

  • Why is one of my radiators not working?
  • Why are all of my radiators not working?

Radiators are an essential part of a home’s central heating system during colder months. As winter approaches, a working radiator is the difference between a cosy or chilly home. A cold radiator is not only a nuisance, but can also be a sign of larger issues in the system such as a broken boiler or pipe blockages and leaks.

a woman sat on her phone in her living room

Why is one of my radiators not working?

If you find that one radiator is not getting hot but the rest of your heating system is working correctly, the best place to start is with the radiator itself. There are usually two types of cold radiators:

  • Radiators that are cold in parts but warm in others
  • Radiators that are completely cold

Carefully inspect the radiator to see which areas, if any, are warm.

Check for trapped air in the system

If parts of the radiator are warm but in others it’s cold it is likely that trapped air is blocking the passage of hot water. The solution is to bleed the affected radiators.

The process of bleeding a radiator involves opening the valves of the radiator to release trapped air. You will need to first turn off the heating and wait for the radiators to cool down completely, before opening the bleeding valve with a radiator key. You will then hear a whistling sound as trapped air leaves the system. As soon as the whistling stops and only water is exiting from the valve, close the valve back up with the radiator key and repeat the process with any other affected radiators.

For more information, check out our guide to bleeding radiators.

Check your radiator valves

If the entire radiator is not getting hot and showing no signs of trapped air, you should then check the valve on your radiator to make sure it is on the right setting. If you have a manual valve, you should be able to see the setting it is on and make any necessary adjustments.If you have a thermostatic valve, it should be set to monitor the temperature of the radiator and automatically adjust it to maintain a regular room temperature. It may be that the thermostatic valve is set to an incorrect temperature, which can also be easily adjusted.If you have inspected the valves on your radiator and it is still not working, it may be that the valve has become blocked by sludge or limescale.

The best solution is to call a professional heating engineer who will be able to assist you with unblocking the radiator. The engineer may discover that the radiator itself is decaying and in need of replacing.

Why are all of my radiators not working?

Check your boiler

The most common reason for a cold radiator is if the boiler itself is not working. Boilers can break down over time, sometimes suddenly and without warning. The first step you should take if your radiators are not heating up is to check if your boiler is working as it should. It may be that the boiler is only set to heat hot water and not heating.

Alternatively, the boiler may be set to turn on at an unexpected time, or only heat radiators to a certain temperature. Check your boiler display module to check the current settings. If the settings are all set correctly, it may be that your boiler is faulty. Boiler parts can become faulty over time or if the boiler has not been regularly serviced, causing issues that force the boiler to shut down.

Check your boiler panel to see if an error code is showing. Cross reference this code with your boiler manual, as each manufacturer will have a different code for a particular problem. In most cases the fault must be rectified by a Gas Safe Registered (GSR) engineer.

Check your water pressure

If your boiler appears to be in working order, you should look at your water pressure. You will have a pressure gauge, a display that shows the level of water pressure being sent to the boiler from the mains, usually located directly where the water supply is connected to your boiler. The correct level of pressure is usually set at 1 bar; if the pressure appears lower than this, you should contact a professional.


  • If a radiator is cold in parts but warm in others it is likely that trapped air is at fault. Bleeding the affected radiator should solve the issue.
  • If the entire radiator is not warming up, it is likely you will need to bleed the affected radiator, Alternatively it may be that there is an issue with the valves.
  • If multiple radiators are not turning on the issue might be boiler related. Inspect the display module to see if there is a fault.
  • If everything appears to be working correctly, check the manometer to see if it is set to the correct level of water pressure.
  • Call a Gas Safe Registered engineer to resolve the problem if you are unable to successfully repressurise your boiler.