Here’s Why It Happens and What You Should Do
There’s nothing worse than coming home to find your boiler won’t turn off even when you’ve switched off the heating or hot water. It’s not just frustrating; it can also be dangerous and costly if left unchecked.
If your boiler is constantly running, you’re not alone. Many homeowners experience this issue and while it might seem minor at first, it’s a clear sign something isn’t quite right with your system.
In this guide, we’ll explain why your boiler won’t turn off, what you should (and shouldn’t) do, and when it’s time to call a Gas Safe engineer to fix it safely.
Why Your Boiler Won’t Turn Off
If your boiler keeps running even after you’ve turned off the heating or hot water, there are a few common causes behind it. Some are electrical, others mechanical, but all require careful inspection, ideally by a qualified professional.
Here are the most likely reasons:
1. Faulty Thermostat
A broken or miscalibrated thermostat is one of the most common reasons a boiler stays on. If your thermostat isn’t accurately reading the temperature in your home, it may constantly “tell” your boiler to keep heating.
Sometimes, the issue is as simple as a flat battery or a loose connection. Other times, it could be a sign the thermostat needs replacing.
2. Stuck or Faulty Motorised Valve
Your heating system uses motorised valves to control the flow of hot water. If one gets stuck in the open position, hot water will keep circulating through your radiators even when you’ve turned everything off.
This is a common fault in older heating systems and one that needs a professional fix.
3. Boiler Timer or Programmer Fault
If your boiler timer or programmer is faulty, it might be sending incorrect signals to your system, keeping it on continuously.
Power cuts, wiring issues, or even outdated settings can cause this. In many cases, reprogramming or replacing the timer solves the issue.
4. Stuck Relay or Control Board Issue
Modern boilers use electronic control boards to manage their functions. If a relay switch inside becomes stuck or damaged, it can trap your boiler in the “on” position.
This type of fault usually needs diagnosis and repair by a Gas Safe registered engineer it’s not something you should attempt yourself.
5. Hot Water Demand Sensor Fault
Combination boilers (combi boilers) can sometimes misread a hot water demand signal, even when no tap is open.
This can make the boiler run constantly, wasting energy and potentially overheating components.
Why You Shouldn’t Try to Fix It Yourself
When your boiler won’t turn off, it’s tempting to start investigating maybe remove the cover, poke around the valves, or reset the controls. But this can be risky.
Boilers are complex systems that handle gas, electricity and water under pressure. A wrong move could make the problem worse, cause leaks, or even create a gas safety hazard.
If you’re not Gas Safe registered, you should never attempt to repair or open your boiler. It’s not only dangerous it’s also illegal.
Instead, here’s what you can safely do before calling a professional:
Turn off the boiler’s power at the isolation switch (usually located nearby).
Turn off the central heating control or thermostat, if possible.
Wait and observe if the boiler continues running, make a note of any noises, error codes, or flashing lights.
Call a qualified engineer for a proper inspection.
How a Gas Safe Engineer Can Fix It
When you call in a Gas Safe engineer, they’ll carry out a full diagnostic to find out exactly why your boiler won’t turn off.
Here’s how they’ll typically handle it:
Inspect the thermostat and wiring to ensure correct communication between controls and the boiler.
Test motorised valves for movement and electrical continuity.
Check the control board and relays for stuck switches or burnt-out components.
Review the timer/programmer to confirm it’s working correctly.
Test sensors and safety controls to ensure the system shuts off properly when it should.
Once the issue is identified, your engineer will carry out the necessary repair or replacement safely, efficiently, and in line with Gas Safe standards.
Don’t Risk It Get It Fixed Professionally
A boiler that won’t turn off isn’t just inconvenient. It’s a symptom of a deeper issue that could lead to:
Higher energy bills – your boiler is burning fuel constantly.
Component damage – overheating or stress on parts.
Potential safety hazards – gas leaks or electrical faults.
At Plumbing Immediately, the Gas Safe registered engineers we connect you with, can quickly diagnose and fix the problem, ensuring your boiler operates safely and efficiently again.
We work with all major boiler brands, and we’re available for same-day call-outs in emergencies.
Call Us Now For Gas Safe Engineers 24/7
If your boiler won’t turn off, don’t ignore it and definitely don’t try to fix it yourself.
Call us for fast, professional boiler repair and peace of mind. We’ll make sure your boiler is safe, efficient and working exactly as it should.