Quick answer
Work through the safe checks in order: power supply, boiler display, thermostat, timer, pressure, gas supply to other appliances, fault code, frozen condensate, a single reset attempt and any recent changes to controls. If the fault involves gas, combustion, the flue or internal components — or you smell gas — stop and contact a Gas Safe registered engineer.
When the heating stops, a surprising number of call-outs turn out to be something simple — a tripped switch, a flat thermostat battery, a programmer that reset after a power cut. Working through these checks in order tells you whether you have a five-minute fix or a genuine boiler fault, without going anywhere near the parts of the appliance only an engineer should touch.
1. Power supply
Check the fused spur or switch next to the boiler is on, and look at the consumer unit for a tripped breaker or RCD. If a breaker keeps tripping, leave it off and call an electrician or heating engineer — repeatedly resetting it is not safe.
2. Boiler display
A blank display usually means no power. A lit display with a fault code means the boiler has detected something and locked out. A normal display with no response to demand usually points to controls rather than the appliance.
3. Thermostat
- Is it calling for heat — set it several degrees above room temperature and listen
- Have the batteries died in a wireless or smart thermostat
- Has a smart thermostat lost its pairing or its schedule after an update
4. Timer or programmer
Power cuts and clock changes routinely knock programmers back to a default schedule or the wrong time. Switch to a constant or override setting temporarily — if the boiler fires, the schedule is your answer.
5. Boiler pressure
Check the gauge or digital pressure reading. Low pressure is one of the most common reasons a boiler refuses to fire, and topping up is a safe homeowner task when done properly.
Pressure reading low?
Our step-by-step guide shows how to repressurise safely using the filling loop.
How to top up boiler pressure6. Gas supply
Check other gas appliances, such as a hob, are working. If nothing gas-fired is operating, the issue may be the supply or a prepayment meter rather than the boiler. Do not attempt any work on gas pipework or meters.
7. Fault code
Note the exact code shown and check it against your own boiler's manual. Codes are manufacturer-specific — the same characters can mean completely different things on a Worcester Bosch, a Vaillant, an Ideal and a Baxi. Having the code ready when you call speeds up diagnosis considerably.
8. Frozen condensate pipe
In freezing weather, a boiler that stopped overnight and gurgles when it tries to fire very often has a frozen condensate pipe. If the pipe is safely accessible at ground level, warm water can clear it.
9. Reset — once
Most boilers have a reset button. Use it as described in the manufacturer's instructions, once. If the boiler locks out again, it is detecting a genuine fault and repeated resets can make matters worse. Stop there.
10. Recent changes
Has anything changed recently — a new smart thermostat, a power cut, decorating near the controls, work elsewhere in the house, a zone valve or motorised valve replaced? Recent changes are a frequent cause, and they are the first thing we ask about.
When to stop troubleshooting
Stop immediately and contact the appropriate professional or emergency service if you smell gas, see scorching or sooting around the boiler, notice water leaking from the appliance, or if the boiler locks out repeatedly. Anything involving gas, combustion, internal components or the flue is engineer-only work.
Boiler still not working?
Gas Safe registered diagnosis and fixed-price repairs across Tamworth, Lichfield, Sutton Coldfield, Walsall and Birmingham.
Book a boiler repairWhen to call a professional
Safe homeowner checks stop at pressure gauges, radiator valves, controls and visible pipework. Anything involving gas, combustion, the boiler casing, the flue or internal components is work for a Gas Safe registered engineer. If you smell gas, follow the appropriate emergency gas safety guidance and do not attempt to work on the appliance.
Call 07881 963508The Betaflo recommendation
A clear, safe order of checks for a boiler with no heating or hot water, and the point at which troubleshooting should stop. If you'd like a second opinion before spending money, speak to us first — we'd rather tell you your boiler is fine than sell you something you don't need.
Frequently asked questions
Why do I have hot water but no heating?
That usually points to controls, a diverter valve or a motorised valve rather than the burner itself, because the boiler is clearly firing for hot water.
Should I keep pressing reset?
No. One reset attempt is reasonable. A boiler that locks out again has found a genuine fault and needs diagnosing.
How quickly can an engineer attend?
Call us and we will give you a realistic slot — during cold snaps demand is high, so getting the fault code and symptoms to us early helps.
About the author
Betaflo Heating UK
Betaflo Heating UK is founded and run by Miles Davis and Sam Boyle, Gas Safe registered heating professionals installing, servicing and repairing boilers across Tamworth, Birmingham and the surrounding areas. Our guides are written from the work we do in customers' homes every week. More about Betaflo.
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