What To Do When Your Central Heating Won't Turn Off

Most heating issues are concerned with the heating not turning off, but you might find that your heating doesn’t actually want to turn off. 

Here’s a curious heating issue that some people encounter - your heating turns on but doesn’t turn off

Most heating issues are concerned with the heating not turning off, but you might find that your heating doesn’t actually want to turn off. 

If your heating doesn’t turn off, you’re more likely dealing with an electrical or settings fault rather than a mechanical one. 

Here’s what to do if your heating won’t turn off. 

Why won't your central heating turn off?

If your central heating doesn’t turn off in the usual fashion, bear in mind that you can manually shut off the power to the boiler if you need to.  

Many modern combi and system boilers have a power switch that you can simply switch off to turn off the heating. You can shut off individual radiators in a conventional system by turning them off at the TRV and lockshield valves. 

If you need to shut your central heating down in an emergency, you can shut off the gas supply to the boiler and house. If you smell gas and suspect a severe fault, phone your energy supplier’s emergency line as soon as possible. 

Here are the four main reasons why your heating doesn’t turn off:

1: The Thermostat Is Faulty 

The thermostat’s job is to relay your home’s air temperature to the boiler. Older thermostats take the form of a small rotary dial, whereas newer ones are LCD or touchscreen. 

Above: Conventional rotary thermostat. 

Thermostats are quite simple. You set the desired temperature on the thermostat, your home heats up, and when the target temperature is obtained, the heating switches off. 

However, settings issues and faults can prevent the thermostat from signalling the boiler to turn off. If the thermostat isn’t working correctly, the boiler may not switch off. 

Turn your thermostat to zero before you try anything else and wait to see if that turns your heating off. If that fails, check the settings carefully. 

‘Finger faults’ are common with modern touchscreen thermostats and programmers, which have many different settings and options. If you have a smart home-enabled thermostat, check the settings in your smartphone app. 

Black and round Smart Nest Thermostat mounted on white wall
Above: Smart thermostat

  • Firstly, try changing the batteries. If that has no effect, the thermostat might be suffering from faulty wiring or a broken sensor.
  • If it’s a newer digital thermostat, reset it and start over again. 
  • If you’ve installed it recently, run through the setup process again. 
  • Lastly, if your thermostat is smart home-enabled, ensure that none of your devices is keeping your heating on. 

2: Programmer or Timer Defects

The boiler programmer or timer may also be faulty. Bear in mind that the programmer and thermostat may be separate or part of the same unit. 

Firstly, check the programmer or timer unit to ensure the settings are correct. The time should match the actual time. You can also try resetting the entire unit if possible. 

If everything looks in order, there may be an issue with the main circuit board (MCB), meaning the unit is failing to instruct the boiler to switch off. 

A heating engineer will be able to test and bypass the programmer/timer/thermostats to find out which one is at fault. 

  • The programmer/timer may be the same unit or might be separate. 
  • Ensure all settings are correct and that the time is right. 
  • Try resetting the unit and dialling in the settings again. 
  • Our heating engineers should be able to test and bypass the unit(s) to see where the issue is. 

3: Issues with the valves

Boilers contain motorised valves that control hot water flow to the heating system. The boiler communicates with the valves and tells them to close when the heating is switched off.

Motorised valve of a boiler
Above: 3-way motorised valve

 However, if the valves fail, the heating won’t switch off when instructed to do so. 

Motorised valves can either break or become locked in the ‘open’ position. A heating engineer should be able to quickly tell whether the valve is the issue. Replacing the valve or its components should fix the issue. 

  • Boilers contain motorised valves that open/close the flow of hot water. 
  • These valves can break or become seized. 
  • Replacing the valves or system diaphragm should fix the problem. 
  • This is a job for one of our heating engineers. 

4: Issues with boiler wiring

Rarely, the boiler’s own internal circuitry can fail. For example, if water enters the system via a leak, it might short out the electrics and prevent the boiler from shutting off the hot water supply. 

If this or something similar happens, your boiler will likely display an error code. Check this error code against the manual to get an idea of the fault. If you suspect an electrical issue, you’ll need to call a heating engineer. 

  • Rarely, the boiler’s internal wiring may fail. 
  • Leaks or short circuits could be the issue. 
  • Check for boiler error codes. 
  • Call one of our heating engineers. 

How to Turn Your Heating Off

Turning off modern boilers is simple; simply locate the power switch and turn it off. In addition, you can often shut off the heating and hot water separately. You can also turn the thermostat down, or turn it all the way to zero to prevent the boiler from heating. 

White boiler with dials and digital display
Above: You can turn the water and heating dials to zero on this boiler.

The procedure for older boilers varies, but most have a dial or switch you can turn off, or turn down to zero. If you’re turning off a gas boiler with a separate hot water tank, it’s best to locate the supply valve on the pipe from the water tank itself and turn that off too.

If you need to turn off your boiler in an emergency, you can shut off the gas at the boiler or the gas isolation valve. 

You can also shut off individual radiators at the TRV and lockshield valves. 

Summary: My heating won't turn off

If your heating doesn’t turn off, the issue probably lies with the programmer/timer/thermostat, which may be different units or part of the same unit. If you have a complex modern programmer, check the settings thoroughly. 

Reset if necessary - ‘turning it off and on again’ can work as well here as it does in other situations! 

Never start disassembling the boiler or other essential components without advice. If you’re unsure of what to do, contact our heating engineers. If the smell of gas accompanies a boiler fault, call your energy supplier’s emergency line. If this doesn't help with your problem discover our the 10 most common boiler problems.

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