Home/Troubleshooting Guide
No Heating Troubleshooting Guide
Losing heating is stressful, especially in cold weather, and the instinct is to want it fixed immediately. A handful of checks take a few minutes and either fix the problem outright or give the engineer a clearer starting point when they arrive. None of this involves opening the boiler itself — that step is for a Gas Safe registered engineer only.
Quick answer
Before calling an engineer, it is reasonable to check pressure, thermostat and timer settings, and whether the boiler is displaying a fault code — these take a few minutes and rule out the simplest causes. Anything involving opening the boiler casing or gas components is not a DIY step; that needs a Gas Safe registered engineer.
Checks You Can Safely Do Yourself
These are checks anyone can safely do from outside the boiler casing — they take a few minutes and rule out the simplest, most common causes before assuming something has actually broken.
- Check the pressure gauge — most boilers need pressure within a specific range (usually marked on the gauge) to fire at all.
- Check the thermostat is set above room temperature and the programmer has heating scheduled for the current time.
- Check the boiler display for a fault code or error light, and note it down — this speeds up diagnosis considerably.
- Check nearby switches and the fuse spur for the boiler have not been accidentally turned off.
- Check whether it is heating only, hot water only, or both that have stopped — this detail matters for diagnosis.
What These Checks Usually Rule In or Out
Low pressure showing on the gauge is one of the more common, and more fixable, causes of a boiler refusing to fire — some systems allow a safe top-up via a filling loop, but if you are not confident doing this yourself, it is a very quick job for an engineer and not worth risking getting wrong.
A fault code, even if you don't know what it means, is genuinely useful information — our fault code reference covers the commonly searched codes for Worcester Bosch, Vaillant, Ideal, Baxi and Glow-worm boilers, and can give you a starting steer on what the code typically indicates before the engineer arrives.
When to Stop and Call an Engineer Immediately
Some situations are not troubleshooting territory at all. If you smell gas, hear the boiler making unusual banging or whistling noises, see a yellow or orange flame instead of blue, or notice soot or scorch marks near the boiler, stop using it and call a Gas Safe registered engineer — do not attempt to investigate further yourself.
Understanding Your Boiler Type Before You Call
It genuinely helps the engineer, and can help you troubleshoot, to know whether you have a combi, system or regular (heat-only) boiler. A combi boiler heats water on demand with no separate tank or cylinder, so no heating and no hot water often share a cause. A system boiler works with a hot water cylinder but no separate cold water tank, while a regular (or 'conventional') boiler works with both a cylinder and a loft tank — on these older setups, heating and hot water faults are more often separate problems with separate causes.
If you're not sure which you have, a combi is usually a single compact unit with no tank anywhere in the property; a cylinder in an airing cupboard points to a system or regular boiler. This one detail changes which faults are even possible, and it's worth knowing before you call.
Fixed price before we travel
Every visit is priced as a clear fixed fee — not an open-ended hourly meter that climbs while someone guesses.
Fault-code confirmed, not assumed
A fault-code and pressure check confirms the boiler is genuinely fixed or the defect is genuinely diagnosed, not just assumed from a reset.
Documentation that holds up
Fault codes, parts used and a written report when a managing agent, landlord or insurer needs more than a one-line invoice.
Our services
Related boiler & heating services
London coverage
Available across all 33 boroughs
Same approach from Barking to Richmond. Browse a borough for local housing notes, or send your postcode for a fixed-price slot.
Frequently asked questions
Is it safe to top up my boiler pressure myself?
On many boilers, yes — there is usually a filling loop with instructions in the manual, and it's a routine task. If you are unsure, or the pressure keeps dropping repeatedly, it's better to have an engineer check it rather than repeat the top-up indefinitely.
My boiler is showing a fault code — what should I do?
Note the exact code and check our fault code reference for what it typically indicates for your brand. Some codes point at simple resets, others indicate a fault that genuinely needs an engineer — the code alone tells you which category you're in.
Can I reset my boiler myself if it has locked out?
Most boilers have a reset button and it is generally safe to try once. If it locks out again straight away, or repeatedly, stop resetting it and get it looked at — repeated resets without diagnosis can mask a fault that needs attention.
How do I know if the problem is the boiler or something else?
If the boiler display shows no fault and it appears to be firing, but radiators stay cold, the cause may be elsewhere in the system — a stuck valve, a pump issue, or trapped air. If the boiler itself is not firing or showing a lockout, that points more directly at the boiler.
Got a boiler or heating problem in your London home?
Tell us the symptoms and your postcode. Fixed price, agreed arrival window, confirmed before you book.
Book a boiler repair visit