Boiler Problems
Boiler Flashing a Warning Light? What It Means
Reviewed by our Gas Safe registered engineers · Last updated 21 July 2026
A flashing light or LED usually signals a fault — most often low pressure, a lockout, or a sensor. Note the colour, the pattern, and any code shown, then use the guide below to work out what to do.
Quick answer: A flashing light almost always means a fault has been detected. The most common are low pressure and ignition lockouts, both often fixable at home. If a fault code is showing alongside the light, look it up in our Fault Code Library for the exact meaning. Repeated lockouts, or a gas smell, need a Gas Safe engineer.
Common Causes
What the flashing light is telling you
Match the light to the likely cause below. The colour on the left shows whether it’s usually a safe homeowner check or a job for an engineer. If a numeric code is shown, that’s the most reliable guide.
| The light | Likely meaning | What to do |
|---|---|---|
| Flashing red or blue light | Low pressure or lockout | Check the gauge; repressurise to ~1.3 bar |
| Continuous flashing after a reset | Ignition lockout | Try one reset; if it recurs, book an engineer |
| Flashing alongside a code | A specific fault code | Look it up in our Fault Code Library |
| Amber or orange light | Standby or low pressure | Check the pressure and top up if low |
| Flashing in cold weather | Frozen condensate pipe | Thaw the external pipe, then reset |
| Flashing with no heat or hot water | Sensor or PCB fault | Needs an engineer to diagnose |
Safe Checks
What you can safely check
Safe to check
- Note the light’s colour, its flashing pattern, and any code shown
- Check the pressure gauge and top up to ~1.3 bar if it’s low
- In winter, check the external condensate pipe hasn’t frozen
- Try one reset following the boiler’s instructions
Stop and call us if…
- You can smell gas — leave the property and call 0800 111 999
- The light returns immediately after one reset
- There’s a burning smell or the boiler is very hot
Engineer Insight
What we usually find
Manufacturers use flashing lights and LED patterns to flag faults, but they vary hugely between brands — a red flash on one boiler means something different on another. Where a numeric code is shown, that’s the reliable guide. We keep brand fault-code references to hand, so a quick call with the code and light pattern often tells us what’s involved before we arrive.
Costs
What repairs typically cost
Typical North London guide prices — you’ll always get an upfront quote before any work starts.
FAQs
Boiler warning lights — your questions answered
What does a flashing light on my boiler mean?
It signals a detected fault. The most common are low pressure and ignition lockouts. The colour and pattern vary by brand, so check your manual or the code shown for the exact meaning.
My boiler is flashing but still works — should I worry?
It’s worth investigating. Some lights indicate a minor issue like low pressure that’s easy to fix; others warn of a fault that will soon stop the boiler. Don’t ignore a persistent flashing light.
How do I find out what the code means?
Note the exact code and check it in our Fault Code Library, which covers Worcester, Vaillant, Ideal, Baxi and more by brand.
Can I stop the light by resetting?
Resetting once can clear a temporary lockout. If the light returns after a single reset, don’t keep resetting — book an engineer to find the underlying cause.
Is a flashing boiler light an emergency?
Usually not, but if it comes with a gas smell, a burning smell, or no heat in very cold weather, treat it as urgent — turn the boiler off and call us.
Related
Keep troubleshooting
The reliable way to decode a warning — look up your exact code by brand.
Browse codesPressureLow Boiler PressureThe most common reason for a warning light — and how to fix it.
Read guideBoiler ProblemsBoiler Not Igniting / LockoutWhen the flashing light means an ignition lockout.
Read guideBoiler ProblemsBoiler Not Turning OnIf the light is off and there’s no response at all.
Read guidePressureHow to Repressurise a BoilerClear a low-pressure warning by topping up to 1.3 bar.
Read guideBoiler ProblemsBoiler Problems HubAll our boiler troubleshooting guides in one place.
Browse guidesBrowse all Boiler Problems guides, or head back to the Help & Advice Centre.
Not sure what the light means? Send us the code.
Call with the light pattern and any code showing, and we’ll tell you what’s likely involved — then book a Gas Safe engineer if it needs one.
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