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Radiator Not Getting Hot? Here’s Why (and How to Fix It)

A radiator is an essential heat exchanger designed to transfer heat from one medium to the other. An intact radiator should be naturally hot, but sometimes it may fail to heat up for various reasons.

To fix your radiator that’s not getting hot, check the radiator valves, if any other radiators aren’t hot, whether the boiler is on and functioning accurately, ensure the heating settings are correct, inspect for trapped air and bleed the air out, clean the radiator, and fit a boiler filter

This article will discuss possible reasons for the radiator not heating up and various ways in which these problems can be fixed. If you’re ready to troubleshoot your radiator and remedy its issues, please continue reading. 

Radiator not getting hot

Check the Radiator Valves

If your entire radiator is cold, its valves could be a problem. The valves include the thermostatic, lockshield, and manual valves that usually join a vertical pipe with a horizontal one. In most cases, the thermostatic valves do seize up, causing the radiator to stop heating up. In such a situation, the valves seem open, but they’re closed.

If your radiator has a lockshield or manual valve, it could be a problem with adjustments.

Additionally, rusting, internal corrosion or limescale build up in the system can block the valves. If the valves become blocked, then your radiator will not get hot. Besides the radiator not getting hot, other signs of blocked valves include hot pipes (not radiator), noisy radiators, and pinhole leaks.

How to Fix

  • Use your bare hands to adjust the thermostatic valve, or a spanner/valve adjust to tweak the lockshield and manual valves.
  • Conduct a professional radiator power flush.
  • Replace the valves and drain down the central heating circuit to ensure it’s working.
  • For a seized up thermostatic valve simply:
    • Unscrew the top part of the valve. 
    • Unscrew the round knurled ring.
    • Push up and down the round metal pin at the top just a few millimeters. 
    • If it’s already seized shut, try tapping it gently, and it’ll free up.
  • Opt to hire a professional to help you fix the problem correctly. 

Watch the below video to understand how you can properly fix a radiator valve by yourself:



Check Whether Other Radiators Are Hot

Before you get to work on the radiator that isn’t getting hot, consider checking whether other home radiators are heating up. In case all your radiators aren’t hot, then the central heating system, plumbing/pipework, or boiler might have a problem. If one radiator is cold, it means that hot water isn’t reaching that particular radiator. 

How to Fix

  • Make sure that the valves are open (they should be completely anticlockwise).
  • If the valves are stiff, unscrew the cap to reveal the square shaft and use a spanner to open it. 
  • If all the radiators in your home are cold, consider calling an expert for proper servicing.

The following video will help you to adequately understand how to turn your radiator valve anticlockwise:

Check Whether the Boiler Is On and Functioning Perfectly

If you find out that all your radiators are cold, the problem could be with the central heating system. This means if the entire circuit isn’t working running correctly, the radiators won’t heat up at all. In this case, the pilot light can be off, sound unhealthy, or display an error code. Apart from that, the radiator may fail to get hot if the system’s pressure is either too high or too low.

How to Fix

  • If the system is off, switch it on
  • Try to reset the boiler
  • Check your pressure gauge. If you find high or low pressure, use your boiler user’s manual instructions to fix the issue. 

Ensure the Heating Settings Are Correct

Incorrect heating settings may sound obvious, but it’s a common cause of radiator not getting hot. Failure to set your boiler for heating or hot water dispensing does cause the radiator to remain cold even if the system is running. 

On the other hand, some boilers have a “summer mode.” This gives you hot water without running the central heating circuit, which creates a possibility of a radiator not getting hot.

How to Fix

  • Check the heating settings on your boiler and ensure it’s set for hot water or heating.
  • If your heating system is on a timer, ensure the timer is set correctly and working perfectly.
  • If you’re using a wireless thermostat, ensure they’re communicating effectively with your boiler.
  • Your boiler has its own temperature setting, which you may need to increase.

Watch the below video to understand how to use your boiler heating system:

Inspect for Trapped Air and Bleed the Air Out

Trapped air is another reason why your radiator isn’t heating up. If you’ve just switched on your heating system after the summer, there can be air trapped in the radiators. This air causes the radiators to become warm at the bottom while remaining cold at the top.

Additionally, air can get trapped in your radiators due to installing your pump right above the supply tank, accumulation of hydrogen caused by rusting, and leaks.

How to Fix

To get rid of trapped air in your radiator, you’ll need to bleed it. Follow these steps to check and bleed the air out of your radiator:

  1. Turn the heating on.
  2. Identify the radiator (s) that need bleeding.
  3. Turn off the heating and let your radiator cool (if it’s warm at the bottom).
  4. Locate your radiator’s bleed valve.
  5. Prepare the area with an old cloth/towel.
  6. Open the bleed valve to release the air.
  7. Let the water out.
  8. Close the bleeding valve.
  9. Wipe up the drips.

Experts recommend Direct Hardware radiator bleed key

Radiator Bleed Key Easy Grip Easigrip Clock Type Brass


Clean the Radiator

Over time, rust, grime, and dirt will build up and hip at your radiator’s bottom. This will cause the radiator to get warm at the top and remain cold at the bottom. The sludge below your radiator prevents this area from getting heated adequately. 

How to Fix

  • Turn the system off and let everything cool down.
  • Open the lockshield valve to allow you to dismount the radiator from the wall.
  • Remove the thermostatic valve and bleed the radiator.
  • Take the radiator outside.
  • Run clean water through the unit. Do this by attaching a hose to the valve outlets.
  • You can also hire a power-flush service for professional unit cleaning.
  • Use a central heating inhibitor to help break pieces of limescale and rust. Experts recommend FERNOX central heating cleaner 

Watch the below video to understand how you can remove sludge from your radiator:

Fit a Boiler Filter

As discussed above, your radiator can fail to heat due to valves and pipes blockage. This occurs because nothing prevents deposits (dirt, rust, etc. present in water and tubes) from reaching the radiator.

How to Fix

  1. Start by cleaning the unit.
  2. Mount it back on the wall.
  3. Fit a boiler filter to catch all the deposits. FERNOX filter 

Fernox 59257 Filter 28mm is a good example of the best boiler filters.


This article discusses why your radiator isn’t getting hot and effective ways to fix the problems. Use the information discussed above to troubleshoot your radiator and implement a suitable approach to fix your unit. If you’re afraid of doing it alone, don’t hesitate to call reliable central heating and boiler professionals for assistance.


  • Steve Rajeckas

    Steve Rajeckas is an HVAC hobbyist with an avid interest in learning innovative ways to keep rooms, buildings, and everything else at the optimal temperature. When he's not working on new posts for Temperature Master, he can be found reading books or exploring the outdoors.

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