--- title: "Common Causes and Fixes for Central Heating Not Working" description: "Central heating not working? Common causes are power, thermostat, pressure or airlocks. Get step-by-step fixes plus a Gas Safe diagnostic visit in South London." published: "2026-08-10T09:00:00Z" author: "Reion Miller" category: "Central Heating" content_type: "BlogPost" intent: "informational" business: "R.W. Miller Plumbing & Heating" gas_safe: "919881" service_area: "South London, Surrey" canonical: "https://rwmiller.com/blog/central-heating-not-working/" markdown_url: "https://rwmiller.com/blog/central-heating-not-working.md" --- # Common Causes and Fixes for Central Heating Not Working > Central heating not working? Common causes are power, thermostat, pressure or airlocks. Get step-by-step fixes plus a Gas Safe diagnostic visit in South London. Central heating not working has five common causes: no power reaching the boiler, a thermostat or control fault, low boiler pressure, an incorrect timer or programmer setting, and trapped air in one or more radiators. When homeowners ask me, “why is my central heating not working?”, I first check whether the fault affects one radiator, every radiator or the boiler itself. That distinction usually tells us whether to look at trapped air and valves, or at pressure, controls and circulation. Central heating not working across the whole house? Start with the power supply, thermostat, timer, boiler display and pressure gauge. If only one or two radiators stay cold, the problem is more likely to be trapped air, a stuck valve or sludge. ## Quick Troubleshooting Check ## 1. Check the Power Supply Check that the boiler’s fused spur is switched on and that no circuit breaker has tripped. If the boiler display is completely blank, the problem may be with the electrical supply rather than the heating system itself. Check whether other electrical appliances are working and whether there has recently been a power cut. Do not remove electrical covers or attempt internal wiring repairs. ## 2. Check the Thermostat Confirm that the thermostat is set above the current room temperature and is in heating mode. Replace the batteries if you have a wireless thermostat. A wireless thermostat may also lose connection with its receiver. If the thermostat appears to be requesting heat but the boiler does not respond, the controls may need to be tested together. ## 3. Check the Boiler Look at the boiler display for a fault symbol or code. Check the pressure gauge while the system is cool. Many sealed systems operate at around 1.0 to 1.5 bar, although the correct range depends on the boiler. Follow the manufacturer’s instructions if repressurisation is required. If the pressure drops again, do not keep topping it up. A leak or boiler fault may require a [professional boiler repair](/services/boiler-repair/). The search phrase “central heating not working but boiler is on” often describes a circulation or control fault. The boiler may still provide hot water while a motorised valve, thermostat, receiver or pump fails to circulate heat through the radiators. Possible signs of a central heating pump not working include hot pipework near the boiler while the radiators remain cold, unusual humming or the boiler firing briefly before stopping. These symptoms can also be caused by air, sludge, closed valves or another circulation restriction. If you have central heating not working but boiler is on, do not remove the casing or repeatedly reset the appliance. Book a [central heating diagnostic](/services/central-heating/) visit so the boiler, controls and circulation can be tested together. ## 4. Check the Timer or Programmer Make sure the heating schedule is set to the correct times and that the programmer is set to “on” or “auto” rather than “off.” A power interruption can reset the boiler clock or heating programme. Check that the displayed time is correct and temporarily select continuous heating to see whether the system responds. Also confirm that the boiler has not been left in summer mode or hot-water-only mode. ## 5. Check for Airlocks and Cold Radiators A radiator that is cold at the top but warmer below often contains trapped air. Turn the heating off, allow the radiator to cool, then release the air slowly using a radiator key. Check the boiler pressure again afterwards. If only one radiator is affected, check that its thermostatic and lockshield valves are open. A cold lower section or heavy central cold patch may indicate central heating sludge rather than trapped air. Our guides to [bleeding a radiator](/blog/bleeding-a-radiator/) and diagnosing a [radiator not heating up](/blog/radiator-not-heating-up/) explain these local faults in more detail. ⚠️ Do not bleed a radiator while the system is hot or attempt to force a seized valve. If several rooms remain cold, the fault is likely elsewhere in the heating circuit. ## When to Call a Heating Engineer Arrange professional help when: - Every radiator stays cold after basic control checks. - Pressure keeps falling after one careful top-up. - The boiler shows a recurring fault code or locks out. - You suspect a pump, motorised valve or internal boiler fault. - The system leaks, bangs or overheats. - Bleeding one radiator does not restore circulation. Signs of a central heating pump not working can be difficult to separate from sludge, trapped air or valve faults without testing the system. Avoid replacing parts based on symptoms alone. When customers ask again, “why is my central heating not working?”, the safest next step is usually to test the system while the fault is present rather than replacing parts by guesswork. ## Book a Central Heating Diagnostic Visit When central heating not working symptoms continue after the basic checks, a diagnostic visit can identify whether the problem is with the boiler, controls, valves or circulation. I provide direct central-heating and boiler diagnostics across South London and Surrey, including [Wandsworth](/areas/wandsworth/central-heating/), Lambeth, Lewisham, Greenwich, Southwark, Bromley, Wimbledon and Clapham. You deal directly with me, [Reion Miller](/about/), Gas Safe registration number 919881, from the first call through to the agreed repair. Call 07375 813996 or [book a central heating diagnostic visit online](/get-a-quote/). ## Frequently Asked Questions ### Can I reset the boiler if the radiators are cold? Follow the user manual and reset it once only if the displayed fault permits it. Repeated resetting does not repair the underlying problem. ### Should I book a boiler service or a repair? A routine boiler service is planned maintenance for a working appliance. If the heating has already failed, book a diagnostic repair visit. ### Why are some radiators hot and others cold? Cold radiators may contain trapped air, have a closed or stuck valve, or suffer from sludge and poor system balance. Start by checking whether the cold area is at the top, bottom or across the whole panel. ## Frequently Asked Questions ### Can I reset the boiler if the radiators are cold? Follow the user manual and reset it once only if the displayed fault permits it. Repeated resetting does not repair the underlying problem. ### Should I book a boiler service or a repair? A routine boiler service is planned maintenance for a working appliance. If the heating has already failed, book a diagnostic repair visit. ### Why are some radiators hot and others cold? Cold radiators may contain trapped air, have a closed or stuck valve, or suffer from sludge and poor system balance. Start by checking whether the cold area is at the top, bottom or across the whole panel. --- *Written by Reion Akim, Owner / Certified Gas Safe Engineer (Gas Safe Registration: 919881). R.W. Miller Plumbing & Heating — South London & Surrey. Call 07375 813996 for a quote.*