Eco Happy (Solar Expert)

Published March 27, 2024

It can be concerning if you notice that your boiler is not switching off when it is supposed to. Fortunately, Eco Happy is here to help.

In this guide, we’ll take a look at the potential causes of your boiler not switching off and three simple steps you can follow to repair the issue.

Why Won’t My Boiler Turn Off?

There can be a few reasons for an overactive boiler. Let’s look at a few of the main reasons behind this problem behaviour.

If you diagnose any of the issues below in your boiler and need some expert help, do not hesitate to contact us at Eco Happy. We offer you an unbeatable quote comparison service so you can find the best local heating engineers to fix your problems.

Faulty thermostat

The thermostat regulates your boiler and heating system temperature using sensors. It will determine when the heating switches on or shuts off as the boiler reaches the desired water temperature.

If there is an issue with the thermostat controls or sensors, the boiler won’t be able to self-regulate. This will lead to it staying on continuously in an attempt to reach the temperature incorrectly indicated by the thermostat. 

Potential issues with your boiler thermostat:

  • Failed temperature sensors
  • Faulty heating system calibration settings

Basic troubleshooting on your thermostat:

  • Turn down the thermostat temperature and monitor if the hot water temperature drops. This way you can determine if the sensors are the issue.
  • Check your thermostat app. Many new boilers make use of a smartphone app. Sometimes, you may mistakenly change the desired temperature settings without knowing it.
  • Check the batteries in your thermostat unit (if they have them). Sometimes, the problem is as simple as your thermostat controller not registering your inputs due to a low battery.

If it is time to replace your device, read our guide on the best smart thermostats and how to connect a wireless thermostat.

Faulty programmer/timer

In most modern boilers, the thermostat will be connected to or integrated with a heating programmer or timer device. These devices allow you to program a range of boiler settings.

If the programmer or timer unit is faulty, it can keep your boiler running, heating your home or water unnecessarily and causing your energy bills to climb.   

You can troubleshoot the programmer and timer with a few simple steps:

  • Restart your boiler and monitor the unit and your hot water (more detail on this below).
  • Monitor your boiler and see if any error codes pop up.
  • If you see no improvement in your boiler’s operation and there are no error codes displayed, it may indicate the issue is with your programmer.
  • Use your boiler manual and perform a factory reset on the programmer. The method for this varies from one unit to another (we will go into more detail later in this article). You can also read our helpful guide on how to reset your boiler.

Faulty valves

Water flow in a boiler and heating system is managed by a collection of motorised valves. These valves are connected to switches that communicate to the boiler when certain valves are in an open or closed position.

Motorised valves can become jammed or malfunction and remain either open or closed, causing boilers to remain on.

For example, the boiler pressure relief valve will activate if your boiler builds up too much pressure. If this valve is on the fritz and stuck in an open position, your boiler will stay on in an attempt to come up to the correct operational pressure.

This is a problem that only a trained heating engineer or Gas Safe engineer can resolve.

Wiring issues

Wiring issues are hard to diagnose and relatively rare. Loose or corroded wiring can cause your thermostat, programmer, valves, or other internal parts to malfunction.

This will lead to your boiler not heating correctly. Faulty wiring can affect your heat exchanger and your heating element. It can even affect the previously mentioned devices like your room thermostat.

Only a boiler engineer or Gas Safe engineer should fix these faults.

How Do I Fix My Boiler Not Turning Off?

You can fix your boiler heating issue by following these three simple steps:

1. Rebooting your boiler

Find your boiler’s control panel and switch it to the off position. Wait a few minutes before you switch it on again.

If you are unsure of the procedure to switch off or reset your boiler, check the instructions in the manual.

 2. Troubleshoot the error codes

Check what error codes your boiler is showing after the reset. Use your boiler manual to look up the codes and their meaning.

You can go online to the manufacturer’s website to find out what these codes mean – or, if you have a Bosch or Vaillant boiler, read our guides to Bosch error codes and Vaillant error codes to help you.

 3. Contact a qualified heating engineer or Gas Safe engineer

If your boiler issue is still not resolved, it’s time to contact a Gas Safe registered engineer or a heating engineer.

It is always good practice to have your boiler serviced annually to identify and repair preventable issues early.


Why is my heating still on when it is turned off?

This is due to a stuck or damaged zone valve. If you have a larger home, the central heating will be separated into areas or zones.

The hot water flow to these sectors is controlled by diverter valves. If there is an issue with a motorised valve, you may find that one room gets warmer or colder than the others.

Is it safe to turn off the boiler at the mains?

It is safe to turn your boiler off at the mains. First, switch off your boiler manually at the unit and make sure you have closed the water mains to minimise the risk of further issues like leakage.

After you do this, double-check your boiler manual to see the manufacturer’s recommended operating procedure.


The most common reasons why a boiler won’t turn off are thermostat or programmer/timer failure.

Resetting or rebooting your boiler can fix these issues unless the devices are at fault and it is not a programming or user error. For example, a faulty motorised valve would require a boiler engineer to fix it.

For info on boiler troubleshooting, or if you are in the market for a replacement boiler – or have any other hot water issues – visit us at Eco Happy. We provide our customers with the absolute best quote comparisons for great deals and service from your local Gas Safe heating engineers.

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