Central Heating Not Working in Alton - What to Check First

Published September 2026 | Central Heating Not Working What to Check First

Your boiler's on, the display looks normal, but the radiators are stone cold. Or maybe the boiler won't fire at all, and you're standing in your Alton kitchen wondering whether to start working through a checklist yourself or just pick up the phone. Which approach actually makes sense?

The honest tension here is this: some heating faults take five minutes to fix without any tools, and calling an engineer for those feels like an expensive way to be told your timer was off. But other faults that look simple on the surface are actually masking something more serious, and the wrong DIY intervention can delay a proper repair or create a safety risk. Knowing which situation you're in is the whole game.

Option A - Running DIY Diagnostic Checks Yourself

DIY diagnostic checks mean working through a structured list of things you can safely inspect and adjust without any technical training or specialist equipment. This isn't about opening the boiler casing or touching the gas supply - it's about ruling out the simple causes that account for a large proportion of heating callouts across Alton and Hampshire every winter.

What this involves

A proper self-check typically covers five areas in this order:

1. Thermostat and timer settings - Check your room thermostat is set above the current room temperature, and that your programmer or timer is set correctly. A power cut, a clocks change, or someone accidentally adjusting the timer are among the most common causes of heating failures our engineers encounter.
2. Boiler pressure - Most modern combi boilers need to sit between 1 and 1.5 bar when the system is cold. If the pressure gauge is reading below 1 bar or has dropped into the red zone, the system needs repressurising via the filling loop. Your boiler manual will show you how - it takes about two minutes and requires no tools.
3. Power supply - Check the boiler has power. Look at the spur switch on the wall near the boiler, and check your consumer unit for a tripped circuit breaker. Boilers share circuits with other appliances in some older Alton properties, and a trip elsewhere can take the boiler offline.
4. Pilot light or lockout indicator - On modern boilers, look for a fault code or lockout light on the display. Note down any code shown and check your manual - manufacturers like Worcester Bosch, Vaillant and Viessmann all publish fault code guides online, and many codes point to simple resets.
5. Frozen condensate pipe - In cold weather, the condensate pipe (the plastic pipe running from the boiler to an outside drain) can freeze solid and trigger a lockout. This is one of the most common causes of heating failure during cold snaps and is something most homeowners can deal with themselves using warm water poured over the pipe.

Pros of the DIY approach

The main advantage is speed and cost. If your heating has stopped because the programmer got knocked off schedule or the pressure has dropped slightly, you can fix it in under ten minutes at no cost. There's also value in working through the checks even if you can't resolve the fault yourself - it means you'll have useful, specific information ready when you do call an engineer, which can shorten the time they spend on site and reduce your overall bill.

Cons of the DIY approach

The risk is misdiagnosis. If you assume the fault is low pressure and repressurise the boiler, but the real cause is a slow leak somewhere in the system, you've masked a symptom without finding the problem. The pressure will just drop again. Some homeowners also feel uncomfortable around boilers, and that discomfort is worth listening to. If you're not confident in what you're looking at, there's no value in pushing on - the DIY-first approach only works if you can stay methodical and stop when you've reached the limit of what's safe to check.

Option B - Calling a Gas Safe Registered Engineer Straight Away

Calling an engineer immediately means skipping the self-diagnosis and getting a qualified professional to assess the system from the outset. In the UK, any work involving the gas supply or sealed boiler components must be carried out by a Gas Safe registered engineer - this is a legal requirement, not just best practice.

What this involves

A heating engineer will typically start with a full system assessment rather than going straight to the boiler. This means checking the boiler, the controls, the radiators, the expansion vessel, the pressure relief valve and the visible pipework. On a first diagnostic visit, you can expect the engineer to spend 45 minutes to an hour before any parts are ordered or repair work begins.

Using the Voltrade GoFIX diagnostic tool when you book can speed this process up significantly. You're prompted to describe what the boiler display is showing, any sounds you've noticed and whether the problem affects heating only or hot water as well. That information reaches the engineer before they arrive, which means they commonly come prepared with the most likely parts already in the van - cutting out a second visit to collect components.

Pros of calling an engineer immediately

The clearest advantage is that you get a properly qualified professional assessing the system without the risk of accidental damage or misdiagnosis. For anything involving the gas valve, the heat exchanger, the fan, the pump or the printed circuit board, an engineer is the right call every time. Engineers also carry calibrated test equipment that can detect flue integrity problems and combustion issues that are completely invisible to an untrained eye.

Cost is often more predictable than homeowners expect. A standard boiler diagnostic visit in Hampshire typically costs between 60 and 120 pounds depending on the engineer and the nature of the callout. If the fault turns out to be simple, you've paid a modest amount for professional certainty. If it's more complex, you've got a proper diagnosis to build from rather than a series of guesses.

Cons of calling an engineer immediately

The main drawback is availability. During cold snaps - which do hit Alton and the wider Hampshire area with some reliability in January and February - heating engineers can be booked out for several days. If the fault turns out to be something like a timer issue, you may have waited days and spent money on a callout that a ten-minute self-check would have resolved for free. There's also the frustration factor: if you're on a tight budget, spending 80 to 100 pounds to be told your system simply needed a pressure top-up is a difficult outcome to sit with.

Side-by-Side Comparison

Which Is Right for Your Situation

The decision usually comes down to what the boiler looks like right now and whether there are any warning signs beyond simply no heat.

Call an engineer immediately if:

• You can smell gas. Don't check anything else - leave the property without using any light switches, and call the National Gas Emergency Service on 0800 111 999.
• Your carbon monoxide detector has activated.
• The boiler is making loud banging, kettling or rumbling sounds - this can indicate a heat exchanger problem in more serious cases.
• There's water leaking from inside the boiler casing.
• The boiler is showing a fault code you can't identify in the manual.
• You've already worked through the basic checks and nothing has resolved it.
• Your boiler is more than 12 to 15 years old and has no recent service history.

Try DIY checks first if:

• The heating has stopped but there's no unusual smell, sound or visible fault.
• The boiler display is showing a low-pressure warning.
• The heating stopped after a power cut or the clocks changed.
• Only some radiators are cold - particularly on upper floors or at the ends of runs - which often points to air in the system rather than a boiler fault.
• The weather has been freezing and you have a condensate pipe running outside the property.

There's a middle path worth considering. Work through the basic checks, note down everything you find including any fault codes, then call an engineer with that information already prepared. You haven't wasted anyone's time, and you've given the engineer a head start that often means a faster, cheaper resolution.

What Alton Homeowners Typically Choose and Why

In our engineers' experience working with homeowners across Alton and surrounding Hampshire villages, most people fall into one of three groups when the heating stops working.

The first group goes straight to the phone. They're not comfortable around boilers, they've had a bad experience with a DIY fix in the past, or they have young children or elderly relatives in the house and can't afford to be without heating while they figure it out. This is a perfectly sensible approach, and there's no criticism in it - knowing the limits of your comfort zone is a form of competence.

The second group works through the checks methodically before calling. These tend to be homeowners who've lived in their property for several years, know where the filling loop is, know their boiler's typical operating pressure and have dealt with a heating fault before. For this group, the DIY-first approach commonly saves an unnecessary callout fee.

The third group - probably the most common in Alton - does a quick initial scan (is there power? does it smell of gas? what does the display say?) and calls an engineer if there's no obvious simple cause. This is arguably the most practical approach for most homeowners: you're not spending an hour working through boiler forums online, but you're also not calling an engineer to tell you the timer was switched off.

Alton's housing stock is varied, with a mix of older brick-built properties running ageing conventional boilers and newer builds with modern combi systems. The age of your boiler is a significant factor. If you've got a unit that's more than 12 years old and it stops working, getting a Gas Safe engineer's assessment is generally the right call even if you suspect a simple cause - older systems often have several issues developing at the same time, and a professional visit gives you a fuller picture of where things stand.

Making Your Decision

Is there any smell of gas or has your CO alarm activated?

If the answer to either of these is yes, stop reading and act immediately. Leave the property without using any switches - including light switches - and call 0800 111 999. This is not a situation for a DIY check or even a routine engineer booking - it's a gas emergency. Every other question on this list only applies once you've ruled this out completely.

How old is your boiler and when was it last serviced?

A boiler under 8 years old that was serviced within the last 12 months is a reasonable candidate for DIY checks first - if it stops working unexpectedly, a simple fault is the most likely cause. A boiler over 12 years old without a recent service is more likely to have a mechanical or component failure behind the problem, and a professional diagnosis is the more appropriate starting point. If you're not sure of your boiler's service history, check whether there's a service record booklet near the unit - boilers from manufacturers like Worcester Bosch, Vaillant and Viessmann typically come with one.

Is the whole house without heat or just some radiators?

Total loss of heating - all radiators cold, boiler not firing - typically points to a boiler or controls fault, and this is where checking the pressure, thermostat and power supply is most useful. If only some radiators are cold, particularly on upper floors or at the ends of long pipe runs, the issue is more commonly air in the system or a balancing problem. Bleeding those specific radiators (opening the bleed valve at the top with a radiator key until water rather than air comes out) is something most homeowners in Alton can do safely themselves without any technical knowledge. If bleeding doesn't help, a system balance or powerflush by a local engineer may be needed.

Do you have a warranty or service contract that covers this?

Many boilers sold in the UK over the last decade come with manufacturer warranties of 5 to 10 years, but these commonly require annual servicing to remain valid. If your boiler is within its warranty period, check the terms before attempting any DIY work - some manufacturers require faults to be reported to an approved engineer rather than resolved independently, and an unauthorised intervention can void the warranty. Similarly, if you have a service contract with a heating company covering Hampshire, check whether emergency callouts are included before paying for one separately. A significant number of homeowners find they're already covered and don't realise it until they've paid for a callout out of pocket.

Frequently Asked Questions

How much does a boiler repair typically cost in Alton?

A diagnostic callout in Alton typically costs between 60 and 120 pounds. Repairs vary widely depending on the fault. Replacing a diverter valve or pressure relief valve commonly costs between 150 and 300 pounds including parts and labour. More significant repairs involving the heat exchanger or printed circuit board can reach 400 to 600 pounds, at which point replacement often makes more financial sense for boilers over 10 years old. Getting a written quote before authorising any repair is always worth doing.

Can I repressurise my boiler myself without a Gas Safe engineer?

Yes - repressurising via the filling loop is something most homeowners can do safely without touching the gas supply or opening any sealed components. Your boiler manual will show you where the filling loop is and what pressure to aim for (typically 1 to 1.5 bar). However, if the pressure keeps dropping repeatedly over a short period, that points to a leak or a faulty expansion vessel, and you'll need a Gas Safe registered engineer to find and fix the underlying cause rather than continuing to top it up.

What should I do if my boiler keeps locking out and needs resetting?

A boiler that repeatedly locks out and needs a manual reset is telling you a fault hasn't been resolved. Resetting it once to see if it was a one-off occurrence is fine. Resetting it repeatedly without understanding the cause isn't a good idea - it can mask a worsening fault and potentially create a safety issue. Note down the fault code shown on the display each time, and if the lockout keeps recurring, book a Gas Safe engineer to investigate properly rather than relying on the reset button.

Is it worth repairing an old boiler or should I just replace it?

A commonly used guideline is that if the repair cost is more than half the cost of a new equivalent boiler, replacement is typically the better investment - especially for units over 12 years old. Modern boilers are considerably more efficient than units from a decade or more ago, so a replacement often brings meaningful reductions in running costs alongside better reliability. A Gas Safe engineer can give you an honest assessment of whether your existing boiler is worth repairing or approaching the end of its practical working life.