Thermostat not working: heating won’t turn on or won’t turn off
Quick answer
If your heating won’t turn on or won’t turn off, the cause is often something simple in the thermostat’s settings, batteries, or pairing with its receiver, rather than a wiring fault. Check the mode, setpoint, and batteries first. If heating is stuck on and you can’t control it from the programmer, or the fault keeps recurring, call a heating engineer rather than opening any control housings yourself.
Safety first
- If you smell gas or suspect CO: stop and call 0800 111 999 / seek urgent help.
- If your heating is stuck on and you need it off urgently, you may be able to turn heating off at the programmer/receiver (do not disturb sealed wiring).
- If you’re unsure, avoid opening control housings.
Full checklist: Safety guidance
What you may notice
- The thermostat doesn’t seem to respond when you change the setpoint — may point to flat batteries, a pairing issue with a wireless receiver, or the programmer not enabling heating.
- Heating stays on even when the thermostat is turned right down — can suggest a stuck relay, wiring issue, or valve fault, and is worth treating more urgently if you can’t control it.
- The thermostat works sometimes but not consistently — may indicate low batteries, weak wireless range, or a loose connection.
These are possible explanations, not a confirmed diagnosis. An engineer can confirm the exact cause on inspection.
Safe checks to make, in order
- Check thermostat mode: heat/cool/off, manual vs schedule, and setpoint above room temperature for a ‘turn on’ test.
- If wireless: replace batteries and check the receiver has power (lights/status).
- Check programmer/timer: is heating enabled right now?
- Try a simple demand test: set thermostat high and see if boiler fires for heating.
- If heating won’t turn off: set thermostat low/off and see if boiler continues firing; check whether hot water demand is confusing the observation (combi).
What you can do safely
- Replace batteries if the thermostat uses them.
- Turn the thermostat well above room temperature to test demand.
- Check the programmer or receiver is actually calling for heat.
- Move the thermostat away from obvious heat sources before deciding it is faulty.
When to call a professional
- Heating stuck on and you can’t control it from programmer/receiver.
- Repeated failures or you suspect wiring/zone valve issues.
- You’re not confident with controls or access.
What to tell the engineer
- Which of the checks above you carried out, and what you found at each step.
- Roughly when the problem started and whether it’s constant, intermittent, or linked to specific conditions (e.g. only when heating runs, only in cold weather).
- Any fault code, unusual noise, or visible sign you noticed.
- Whether the issue affects one fixture/radiator or several.
FAQs
My heating won’t turn off — what should I do right now?
Try turning heating off at the programmer or receiver first, without disturbing any wiring or opening control housings. If it stays on and you can’t control it, contact a heating engineer, since a stuck-on system left unaddressed can run up costs unnecessarily.
Could this just be dead batteries?
Yes — this is one of the most common causes for a wireless thermostat that seems unresponsive. Replacing the batteries is a simple, safe first step.
What’s the difference between the thermostat and the programmer?
The thermostat measures room temperature and calls for heat when it’s below the setpoint. The programmer controls when heating is scheduled to run. Both need to be aligned for heating to work as expected.
Should I move my thermostat?
If it’s positioned near a radiator, in direct sunlight, or near a draught, it can give misleading readings. Moving it isn’t always straightforward on wired systems, so it’s worth mentioning to an engineer if you suspect this.
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