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Why Your Heating Won’t Turn Off and How to Fix It

09 October 2025

Is your heating still on when the thermostat is off, or has your boiler won’t turn off even when it should? If your central heating is stuck on, it can be frustrating, waste energy, and increase your heating bills. In this guide, the experts at Shropshire Gas explain common causes, potential solutions, and when to call a Gas Safe engineer.

Common Causes of a Boiler or Heating That Won’t Turn Off

  1. Thermostat Issues

    • If your thermostat is off but heat is on, the thermostat may be faulty or miscalibrated.

    • Wireless or smart thermostats can lose connection to the boiler, causing the system to run continuously.

    • Check the batteries and settings first — sometimes a simple reset can resolve the issue.

  2. Room or Cylinder Stat Problems

    • Radiator thermostats or cylinder thermostats can stick in the “on” position.

    • This can result in the heating still being on even when the thermostat is off.

  3. Wiring Faults

    • Faulty wiring between the thermostat, boiler, and programmer can cause central heating stuck on.

    • Exposed wires, loose connections, or damaged circuits can lead to continuous heating.

  4. Stuck Valves

    • The motorised zone valve or diverter valve inside the boiler may be stuck in the open position.

    • This allows hot water to flow to radiators continuously, even if the thermostat is off.

  5. Programmer or Timer Errors

    • If the timer is incorrectly set, your heating may continue running outside the scheduled times.

    • Resetting or reprogramming the timer can sometimes solve the problem.

Boiler Brand-Specific Issues

Different boilers can have unique quirks when it comes to heating staying on:

  • Vaillant Boilers: Often have issues with stuck diverter valves; a reset or service may be required.

  • Worcester Bosch Boilers: Problems with the PCB or room stat can cause continuous heating.

  • Baxi Boilers: A faulty timer or pressure switch can keep the boiler running unnecessarily.

If you’re unsure of the cause, a qualified engineer can diagnose the issue safely and efficiently.

Why a Boiler Stuck On Is a Problem

  • High energy bills: Continuous heating wastes fuel, increasing your costs.

  • Safety risks: Overheating pipes or radiators can be dangerous, especially in older systems.

  • System wear and tear: Running continuously puts extra strain on components, reducing your boiler’s lifespan.

How to Fix Heating That Won’t Turn Off

  1. Check the thermostat: Replace batteries, reset, or recalibrate.

  2. Inspect radiator valves: Make sure thermostatic valves aren’t stuck open.

  3. Reset the boiler: Switch off at the mains and restart.

  4. Check the timer/programmer: Ensure schedules are correct and match your daily routine.

  5. Call a Gas Safe engineer: If the issue persists, there may be wiring faults, stuck valves, or boiler-specific issues that need professional attention.

Get Help from Shropshire Gas

If your heating won’t turn off or your boiler is stuck on, our Gas Safe engineers can diagnose and repair the problem safely. We cover all major boiler brands, including Vaillant, Worcester Bosch, and Baxi, and provide solutions to get your heating running efficiently again.

📞 Call Shropshire Gas today to book a service or emergency callout — we’ll ensure your heating system is safe, efficient, and fully under control.

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