This winter guide on central heating not working is for UK homeowners who need a clear view of the problem before they spend. It sets out the checks that matter, sensible next steps, and when to arrange a boiler installation, boiler repair, or boiler service. Gas work must be done by a Gas Safe registered engineer.
Key points
- Confirm a genuine call for heat from the thermostat and programmer
- Separate “no heating” from “no hot water” before diagnosing
- Pressure, air in radiators and frozen condensate are top winter culprits
- Zone valves and pumps fail more often after months of light summer use
Map the symptom before you blame the boiler
When central heating not working is the search phrase, the boiler is only one possible culprit. Controls may not be asking for heat. Radiators may be full of air. A zone valve may be stuck on hot water only. A pump may have seized. Starting with a map of symptoms saves money and avoids wrong parts.
While you read, write down whether hot water still works, which rooms are cold, whether the boiler burner lights, and any codes on the display. That notebook becomes the brief for Meraboiler or any other Gas Safe registered firm.
Winter demand exposes weak components that coasted through autumn. Pumps that hummed quietly in October can refuse to start on the first hard frost. TRVs left closed in unused rooms then opened on a cold Sunday night reveal balancing issues that felt fine in September.
Controls first: thermostat, programmer, smart apps
Raise the room thermostat well above current temperature. Confirm the programmer or smart schedule is in a heating window, not holiday or eco-away mode. Replace batteries in wireless stats. Reboot a hung smart hub if the app shows heat demanded but the boiler stays silent. Weather compensation curves can pause the burner while flow temperatures look “low” compared with old on/off systems — see weather compensation controls.
Heating versus hot water split
Hot water working with cold radiators often points to circulation, valves or radiators rather than total ignition failure. No heating and no hot water leans toward boiler lockout, gas supply, PCB or condensate freeze — use boiler not working winter diagnosis in parallel. Combi-only hot water faults belong in no hot water from combi boiler.
- Verify thermostat and schedule are calling for heat.
- Check boiler power, display and cold pressure.
- Look outside for ice on the condensate pipe.
- Feel the boiler flow pipe and a nearby radiator after a call for heat.
- Bleed obvious air-bound upstairs radiators if the boiler is hot but rooms are not.
Circulation problems that look like a dead boiler
A boiler can fire happily while rooms stay cold if water is not moving. Air locks, sludge, seized pumps and stuck motorised valves create that pattern. Cold radiators with a hot boiler need the radiator and circulation path in radiator not heating and how to bleed radiators, not endless boiler resets.
S-Plan, Y-Plan and zone notes
Homes with separate heating and hot water valves can lose heating while hot water still heats the cylinder. Listening for valve motors and checking manual lever positions (where accessible without opening gas compartments) helps an engineer. Do not force valves aggressively.
Vulnerable occupants
If infants, elderly or medically vulnerable people are in a cold home, treat central heating not working as urgent. Use safe temporary heaters, follow our emergency boiler repair steps, and say so when you book attendance.
Need a fixed-price quote? Tell us about the property. Meraboiler Gas Safe engineers cover London and nearby areas.
Winter-specific blockers
Frozen condensate is famous for locking boilers after they have run. External plastic runs ice solid overnight; the boiler senses the blockage and shuts down. Warm water on the pipe (not boiling) can be a temporary thaw if the pipe is safely reachable — full guidance sits in frozen condensate pipe fix and prevention. Low pressure after summer micro-leaks also peaks when systems work harder — see low boiler pressure.
Partial heat: some rooms warm, others freezing
That pattern is rarely a total boiler failure. Bleed air, check TRVs, and consider sludge in single-pipe runs or the index radiator. Balancing may be needed after years of ad-hoc TRV tweaks. If the boiler cuts out when heating finally runs hard, read boiler keeps cutting out in cold weather.
Repair or replace when heating will not return
A failed pump on a healthy mid-life boiler is usually a repair. A corroded heat exchanger on a fifteen-year-old unit during a freeze often favours replacement once temporary heat is in place. Sizing and brand choices still matter — how to size a combi boiler kW and best boiler brands UK 2026 help you ask better survey questions.
How Meraboiler handles this on site
Engineers begin with safety, then match the recommendation to how the household uses heat and hot water. On central heating not working callouts we verify the call for heat, measure temperatures across flow and return, test valves and pumps, and only then discuss major parts. You get assumptions listed on the quote.
If the system is full of sludge, we explain clean options rather than fitting a new boiler onto a dirty circuit without discussion. Where the appliance is near end of life, we say so early using the same tone as our upgrade and replacement guidance.
Costs and practical limits
Daytime diagnosis is cheaper than midnight panic rates. Ask what the first attendance covers before approving a full flush or PCB. Temporary heaters bridge gaps while parts arrive — budget for that separately from the repair quote.
Notes from the Energy Saving Trust and notices on GOV.UK help if chronic underheating is really an insulation or controls problem rather than a broken boiler. Meraboiler quotes separate labour, parts and optional extras. Finance options appear in boiler finance London.
Mistakes that cost money
- Resetting the boiler for an hour instead of checking the thermostat schedule.
- Calling for a new boiler when upstairs radiators only needed bleeding.
- Pouring boiling water on plastic condensate pipework.
- Hiring unregistered help during a freeze because they answered the phone first.
- Ignoring a CO alarm while chasing heat.
Safety first
If you smell gas, leave the property and call the National Gas Emergency Service on 0800 111 999. Never ignore a carbon monoxide alarm. For placement guidance, read carbon monoxide alarm placement for homes with boilers. Keep the boiler case closed for non-gas checks. If water sits near electrics, isolate power at the fused spur only when safe. Gas work must be done by a Gas Safe registered engineer.
FAQs
Summer-idle pumps seize, condensate freezes, pressure sits too low after slow leaks, and schedules that worked in mild weather no longer match occupancy. The first hard frost reveals all of it at once.
Think circulation: air, sludge, pump, valves, TRVs. Bleed carefully, check pressure, then book diagnosis if rooms stay cold. Do not keep resetting an appliance that is already lighting.
You can check controls, pressure top-up on many sealed systems, and bleed radiators. Gas components, sealed combustion checks and internal boiler parts need a Gas Safe engineer.
Opening closed TRVs in cold rooms helps diagnosis. Leaving every valve permanently maxed wastes energy once heat returns — restore sensible settings and consider a proper balance.
Before overnight lows if you can. See winter boiler service — what gets checked and the prepare for winter checklist.
What to do next
Use this page as a working checklist, then speak to a qualified engineer if heat does not return. Further reading sits on the Meraboiler blog and service pages below. Company background is on About Us.
- Boiler not working — winter diagnosis
- How to bleed radiators
- Low boiler pressure — repressurise
- Reduce heating bills in winter
- Boiler repair near me — Meraboiler
- Meraboiler boiler advice blog
- Contact Meraboiler
Book Meraboiler help — surveys, repairs and installations with scopes written down before work starts.
