Central Heating Not Working? Here Is What to Check First
- Michael Beresford
- 5 days ago
- 11 min read
Your central heating not working on a cold morning is one of the most stressful things that can happen in a North West England home. Before you call anyone, there are several checks you can do yourself in under ten minutes that resolve the problem in roughly 30% of callout cases. This guide walks you through every realistic cause, from the obvious to the overlooked, so you stop wasting time guessing and start getting warm again. If the fix is beyond a DIY check, Neptune Plumbing and Heating covers emergency heating repair in Wigan, Leigh, Bolton, Warrington, and Manchester around the clock.
Table of Contents
Quick Takeaways
Key Insight
Explanation
Thermostat settings cause most no-heat calls
A thermostat set below room temperature or stuck in summer mode is the single most common reason central heating appears dead, yet costs nothing to fix.
Boiler pressure below 1 bar stops heating entirely
Most modern combi boilers shut down automatically when pressure drops below 0.5 bar. Repressurise to 1.0-1.5 bar using the filling loop before anything else.
A frozen condensate pipe is winter-specific and fixable in minutes
In sub-zero temperatures, the plastic condensate pipe that exits through an outside wall freezes solid. Pouring warm water over the pipe thaws it without a callout.
Cold radiators with a hot top need bleeding
Trapped air rises to the top of a radiator. Bleeding releases it and restores full heat output across the panel.
Boiler error codes tell you exactly what is wrong
Worcester Bosch, Vaillant, and Ideal boilers all display fault codes. Photographing the code before calling an engineer saves diagnostic time and money.
Gas supply issues affect the whole street, not just your boiler
If your gas hob also will not light, the fault is with the supply. Call the National Gas Emergency number (0800 111 999) rather than a plumber.
Cold bottom, hot top on a radiator indicates sludge
Black iron oxide sludge settles at the bottom of radiators and blocks heat circulation. A powerflush is the correct fix, not bleeding.
Check Your Thermostat First
In practice, about one in three calls we take about central heating not working turns out to be a thermostat issue. The fix takes under two minutes and requires no tools, which makes it the only logical starting point.
First, confirm the thermostat is set above the current room temperature. If your living room is 18 degrees Celsius and the thermostat is set to 17, the boiler will not fire. Raise the setpoint by at least two degrees and wait 60 seconds for the system to respond.
Second, check that the thermostat has power. Battery-operated smart thermostats like Nest or Hive go into a low-power mode when batteries are nearly dead, which can prevent them from sending a heat demand signal to the boiler entirely. Replace the batteries before calling an engineer.
Programmer and Time Settings
After a power cut, your programmer may have reset to the wrong time. If your heating is programmed to come on at 6:30am but the programmer now thinks it is 2:00am, nothing will happen. Check the clock on your boiler programmer specifically, not just the wall clock in the kitchen.
Also confirm the programmer is not set to a holiday mode or summer schedule. This is an extremely common oversight in homes where multiple family members have access to the controls.
Pro tip: If you have a smart thermostat like Hive or Nest, open the app before touching anything physical. The app shows you the current setpoint, the schedule in force, and whether the boiler has responded to a heat demand, which eliminates the guesswork entirely.
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Boiler Pressure and Error Codes
Low boiler pressure is the second most common cause of central heating not working, and it is something most homeowners can fix themselves in under five minutes. Look at the pressure gauge on the front of your boiler. It should read between 1.0 and 1.5 bar when the system is cold. Below 0.8 bar, many boilers lock out completely.
How to Repressurise Your Boiler
Locate the filling loop, which is usually a silver or grey braided hose underneath the boiler connected to two valves. Slowly open both valves to allow mains water into the system. Watch the pressure gauge and stop when it reaches 1.2 bar. Close both valves, then fire the boiler. If pressure drops again within a few days, you have a leak somewhere in the system that needs professional investigation.
Reading Boiler Error Codes
Modern boilers do not just stop working silently. They display a fault code on the LCD panel. Worcester Bosch uses codes like EA338 for ignition failure and E9 for overheating. Vaillant displays F.28 for ignition lockout and F.75 for pressure sensor faults. Ideal boilers use L1 for lockout and F1 for no gas supply detected.
Photograph the error code on your phone before calling for boiler repair in Leigh or anywhere else in the North West. An experienced engineer can often tell you over the phone whether the fix requires parts, saving you a diagnostic visit fee.
"According to the Energy Saving Trust, around 55% of household energy bills come from heating and hot water, making a functioning boiler one of the most financially significant systems in any UK home." Energy Saving Trust
Pro tip: If your boiler keeps losing pressure repeatedly, do not just keep topping it up. Persistent pressure loss points to a system leak, a faulty pressure relief valve, or a failing expansion vessel. Each top-up is introducing fresh oxygen-rich water into the system, which accelerates internal corrosion and will cost you more in the long run.
Pilot Light and Ignition Failures
Older boilers use a standing pilot light that can blow out. If yours has a pilot light window and the flame is out, the boiler will not ignite. Your boiler manual contains instructions for relighting it, but if it will not stay lit after three attempts, the thermocouple is likely failing and needs replacement by a Gas Safe registered engineer.
Modern condensing boilers use electronic ignition and do not have a pilot light. Instead, they attempt to ignite each time a heat demand is received. If the boiler clicks but does not fire, common causes include a dirty flame sensor, a failed igniter electrode, or insufficient gas pressure at the gas valve.
Gas Supply Check
Before assuming a boiler fault, test your gas hob. If no burners will light, the issue is almost certainly with your gas supply rather than the boiler. Check whether your gas meter has tripped or whether a prepayment meter has run out of credit. Call the National Gas Emergency Service on 0800 111 999 if you smell gas at any point.
If the hob works fine but the boiler still will not ignite, the fault is internal. An ignition issue on a combi boiler typically costs between £80 and £200 to repair depending on the part required, which is significantly less than a full boiler replacement.
Frozen Condensate Pipe
This is the most seasonal cause of central heating not working in the North West, and it is almost always fixable without a callout. All modern condensing boilers produce acidic condensate water as a byproduct of their high efficiency. This water drains through a plastic pipe that typically exits through an external wall or into an outside drain.
When temperatures drop below zero, which happens regularly in Wigan, Bolton, and the wider Greater Manchester area during January and February, this pipe freezes solid. The boiler detects a blockage, produces a specific error code (usually indicating pressure or flue issues), and shuts down safely.
How to Thaw a Frozen Condensate Pipe
Find the pipe on the outside of your home. It is typically a 32mm or 40mm white or grey plastic pipe. Pour warm (not boiling) water along the length of the pipe, starting from the open end and working back toward the boiler. Boiling water can crack the plastic, so do not be tempted to speed up the process. Once the blockage thaws, the boiler should restart. Reset it using the reset button and wait for it to fire normally.
If this happens every winter, ask your heating engineer about lagging the condensate pipe with foam pipe insulation. It is a ten-pound fix that prevents the problem entirely.
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Radiators Not Heating Up
If your boiler appears to be working but some or all radiators stay cold, the fault is in the distribution system rather than the boiler itself. The diagnosis depends on exactly which radiators are cold and where the cold area is on each panel.
Cold at the Top: Bleed the Radiator
A radiator that is warm at the bottom but cold or lukewarm at the top has trapped air preventing hot water from filling the panel. Use a radiator bleed key to open the bleed valve at the top corner of the radiator. Hold a cloth underneath. You will hear a hiss of air, followed by water dribbling out. Once only water comes out, close the valve. Check boiler pressure afterwards as bleeding reduces system pressure slightly.
Cold at the Bottom: Sludge and Powerflush
A radiator hot at the top but cold at the bottom has magnetite sludge settling inside it. This black iron oxide builds up over years as the system corrodes internally. Bleeding will not fix it. A powerflush, where a machine forces high-velocity water and cleaning chemicals through the entire system, is the correct treatment. A powerflush for a typical three-bedroom home in the Wigan area costs between £300 and £500 and can extend system life significantly.
One Zone Not Working at All
If an entire floor or zone of the house has no heat, a zone valve is likely stuck or failed. Zone valves are motor-operated and can seize in the closed position, especially in systems that have not been serviced for several years. A heating engineer can replace a zone valve motor in under an hour in most cases.
Pro tip: If you have a system with a hot water cylinder and the upstairs radiators work but the downstairs ones do not (or vice versa), check the zone valves on the pipework near the boiler or cylinder. The two circuits, one for hot water and one for heating, are controlled by separate motorised valves that fail independently.
Comparison of Common Central Heating Faults
Fault Type
DIY Fix Possible?
When to Call a Professional
Low boiler pressure (above 0.5 bar)
Yes. Use the filling loop to repressurise to 1.2 bar.
If pressure drops again within days, a system leak or failed expansion vessel needs professional diagnosis.
Frozen condensate pipe
Yes. Pour warm water on the external pipe to thaw it.
If the pipe freezes every winter, an engineer should lag or reroute the pipe to a more protected location.
Air in radiators
Yes. Bleed the radiator using a bleed key. Takes under two minutes per radiator.
If air keeps returning within weeks, the system is drawing in air from somewhere, which requires investigation.
Magnetite sludge in radiators
No. Partial fixes like removing a radiator create mess and do not clean the rest of the circuit.
A Gas Safe engineer should carry out a full system powerflush with inhibitor dosing.
Boiler ignition failure or lockout
Try a single reset. If it locks out again, stop.
Repeated lockouts mean a component fault. A Gas Safe engineer must diagnose and repair this safely.
When to Call a Heating Engineer
There is a clear line between what a homeowner should attempt and what must be handled by a Gas Safe registered engineer. Crossing that line is not just risky. In the UK it is illegal under the Gas Safety (Installation and Use) Regulations 1998 for anyone other than a registered engineer to carry out work on gas fittings.
Call a professional immediately if you smell gas near the boiler, if the boiler is making banging or kettling noises, if you see black or yellow flames instead of blue, if carbon monoxide detectors are alarming, or if the boiler shuts down repeatedly despite resets. These are not situations where a DIY check is appropriate.
What Heating Repair in Wigan and Leigh Typically Costs
For heating repair in Wigan and the surrounding area, most standard boiler repairs, including replacing a diverter valve, pump, or PCB board, fall between £150 and £400 for parts and labour. Emergency out-of-hours callouts carry a premium, typically an additional £50 to £100 on top of standard rates. A full boiler replacement for a typical three-bedroom semi-detached home in Leigh or Wigan costs between £1,800 and £2,500 fully installed, depending on boiler brand and system configuration.
For boiler repair in Leigh specifically, Neptune Plumbing and Heating operates 24 hours a day with no call centre. You speak directly to an engineer who can assess the fault over the phone and advise whether the repair is possible on the same visit or whether parts need to be ordered, which saves you unnecessary waiting time.
The data consistently shows that annual boiler servicing reduces the likelihood of mid-winter breakdowns by a significant margin. According to Which?, a boiler that is serviced annually is far less likely to develop a major fault than one that runs for three or four years without a check. A service typically costs between £60 and £120 in the North West and takes around an hour.
Frequently Asked Questions
Why is my central heating not working even though the boiler is on?
The boiler being on does not mean it is actively firing. The most common reason is that the thermostat or programmer is not calling for heat. Check that your thermostat is set above the current room temperature and that your programmer is set to a heating schedule that should currently be active. If both are correct, check the boiler pressure gauge and look for any error codes displayed on the boiler panel.
How do I reset my boiler after it stops working?
Most modern boilers have a reset button on the front panel, sometimes marked with a flame and an X symbol. Press and hold it for three to five seconds, then release. The boiler will attempt to relight. If it locks out again within a few minutes, do not keep resetting it. Repeated resets without fixing the underlying fault can damage the boiler's PCB and turn a minor repair into a major one.
Can I fix my central heating myself?
You can safely check and adjust the thermostat, repressurise the boiler using the filling loop, bleed radiators, and thaw a frozen condensate pipe. You cannot legally or safely work on gas pipework, gas valves, or the burner assembly. Any work involving the gas supply to the boiler must be carried out by a Gas Safe registered engineer. This is not a suggestion. It is a legal requirement in England and Wales.
What causes a boiler to lose pressure overnight?
A small pressure drop of 0.1 to 0.2 bar overnight is normal as the system cools and contracts. A drop of 0.5 bar or more overnight indicates a leak somewhere in the system. Common locations include radiator valves, pipe joints behind walls or under floors, and the pressure relief valve discharge pipe on the outside of the property. A heating engineer should pressure test the system to locate the leak before permanent damage occurs.
Why are only some of my radiators cold?
If some radiators are cold and others are hot, the first thing to check is whether the cold ones are at the end of the circuit or on an upper floor. These are the hardest to reach with heat and are the first to show air lock or sludge problems. Bleed each cold radiator in turn. If bleeding does not help and the radiator is cold at the bottom, the system likely has sludge buildup and needs a powerflush. If an entire zone is cold, a failed motorised zone valve is the probable cause.
How quickly can Neptune Plumbing and Heating respond to a heating emergency?
Neptune Plumbing and Heating offers 24-hour emergency callouts across Wigan, Leigh, Bolton, Warrington, Manchester, and the surrounding North West area. Response times depend on current demand and your location, but the team aims to attend emergency heating callouts the same day in most cases. For non-emergency boiler repair in Leigh or heating repair in Wigan, appointments are typically available within one to two working days.
If your central heating is not working right now and you have already worked through these checks without finding the fix, tell us in the comments below exactly what your boiler is doing and which checks you have already completed. We will point you in the right direction.
References
Energy Saving Trust: Home heating efficiency and cost guidance for UK households
Gas Safe Register: Official UK register of legally authorised gas engineers and safety information
Which?: Independent consumer advice on boiler servicing, repairs, and reliability ratings
Statista: UK household energy consumption and heating cost statistics
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