What to do if Radiators are not Working

One or all of your radiators not working is a very common and annoying problem. Most of the time the solution is simple.


Below is a video that might help you. If you're still not warm after watching it then read on for more advice!

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First let’s look at the possible solutions for when none of your radiators are working. Make sure your heating is turned on and that the room thermostat (if there is one) is turned up and calling for heat. If only one radiator is not working, scroll down further for possible solutions.



Below are the possible mechanical checks you should perform to eliminate or find any problems:


  1. Is the boiler alight?

  2. Check that the room thermostat (if present) is switching properly. Only do this if you have a sound knowledge in electrics. Using an electrical tester, test each side of the switch poles when the thermostat is turned up to ensure a live signal is being sent to the motorised valve/pump/boiler according to system.

  3. Motorised Valve Failure? Check that any motorised valves are open. They can be easily identified. Look for a box (either silver of plastic) that is attached to the pipe. Most have an actuator arm on the side that you can move to open and close the valve. If it is easy to move then it is open and working correctly. If it is hard to move or you can hear a slight whirring noise from the valve then it is either not functioning properly or not being called to open when it should be. This is probably the point you should call an engineer.

  4. Is the pump running and are the pump valves open? If there is a motorised valve and it is open check that the pump and boiler are running. Most pumps have a screw on the end of the shaft that can be removed to check that the pump is operating properly. Check that the pump valves are open (fully wound anti-clockwise).



Right, if all of the above mechanical parts are working and you still are not getting any heat to the radiators you will need to check a few other things:


  • Pump valves scaled up? All too often it can come to this. Drain the system and remove the pump and valves. The valves can often clog up due to debris from oxidisation. Clear them out or replace with new ones.

  • Sludge in the heating system? The only way to find this out is to drain the system down, remove each radiator and hose it through outside. If the pipework in the house is sludged up then you are likely to need it power flushed by an engineer.




  • Is the radiator just cold at the top and hot at the bottom? If so the problem is air in the radiator. Using a radiator key to release the air. You should feel the radiator get hot in no time. Remember to top up any lost pressure if on a sealed (pressurised) heating system. Click here to learn how to bleed a radiator.

  • Is the radiator hot at the top and cold at the bottom after 30 minutes of operation? If so then the problem is most likely to be sludge in the radiator. Shut the valves at each end, remove the radiator and hose it though outside till the water runs clear. Click here to learn how to remove radiator sludge.




What we often do as a test is shut all the radiators that are getting hot. Does the trouble radiator then get hot? If so great, you’ve just found the problem – it is just a matter of supply and demand. Usually the solution is simple. Make sure the pump speed is high by adjusting the speed setting on the body of the pump. Now you can perform an operation known as balancing a heating system or allowing an equal supply of heat to each radiator. Click here to find out how to balance a heating system.



If the radiator still does not get hot even when all the others are shut it can still be a simple solution.


If the radiator has a TRV (thermostatic radiator valve) remove the head. Check to see if the pin moves freely. DO NOT hit with a hammer or any other tool as suggested on other websites. You can break the pin or worse still it will fly out of its collar and leave you with a water fountain. All you need to do is gently move the pin up and down with a pair of pliers. Leave the pin in the up position, adjust the removed head to the highest temperature setting and re-attach to the valve body. Now would probably be the time to think about getting new TRV’s. After that check that the lockshield on the other end of the radiator is fully open.


If after trying all of the above you still do not have a hot radiator it could be a blocked pipe in the floor. You’ll need to call an engineer. Good Luck!



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