Boiler Pilot Light Keeps Going Out: Causes, Fixes & When to Call a Engineer
If your boiler’s pilot light keeps going out, you’re not alone. It’s one of the most common boiler complaints from homeowners across Sheffield and the surrounding areas. The good news is that in many cases, it’s a fixable problem — once you understand what’s causing it.
This guide walks through the main reasons a pilot light won’t stay lit, what you can safely check yourself, and the situations where you need a Gas Safe registered engineer rather than a DIY fix.
What Is a Pilot Light and Why Does It Matter?
Older boilers — and some modern condensing boilers — use a pilot light as a small, continuous flame that ignites the main burner when your heating or hot water is called for. If the pilot light goes out, your boiler can’t fire up, which means no heating and no hot water.
Most modern boilers use an electronic ignition system instead, so a “pilot light” issue on a newer unit usually means a different kind of fault. But the result is the same: your boiler won’t start, and you’ll need to work out why.
The Most Common Reasons a Pilot Light Keeps Going Out
1. Faulty Thermocouple
This is the most common cause by far. The thermocouple is a small safety device that sits next to the pilot light and detects whether it’s burning. When it senses the flame, it allows gas to continue flowing. When it doesn’t, it shuts the gas off — a built-in safety mechanism.
Over time, thermocouples wear out. When they do, they may fail to recognise the flame even when it is burning correctly, which causes the gas valve to close and the pilot light to go out.
Signs your thermocouple may be the issue:
- Pilot light relights but goes out as soon as you release the button
- The pilot stays lit for a few seconds then extinguishes
- No other obvious cause (no draught, no gas supply problem)
A faulty thermocouple needs replacing by a qualified engineer. It’s a relatively straightforward job, but it involves working directly with the gas supply — not a DIY task.
2. A Draught or Ventilation Problem
Pilot lights are sensitive to airflow. If your boiler is in a draughty location — a utility room with a gap under the door, a garage, or near a vent — even a small gust can extinguish a flame.
You might notice the pilot light goes out more often in winter, or when external doors or windows are opened nearby.
Check whether the boiler casing is properly fitted and whether there are any obvious gaps that could be letting cold air in. Don’t block ventilation openings though — boilers need adequate airflow to operate safely.
3. Gas Supply Issues
If the gas supply to your home is interrupted or fluctuating, the pilot light may go out and refuse to relight. This can happen if:
- A gas meter fault is restricting supply
- Maintenance is being carried out on the local gas network
- The gas valve on your boiler is partially closed or faulty
Before calling an engineer, check whether other gas appliances in your home (hob, gas fire) are working normally. If they’re not, contact your gas supplier. If only your boiler is affected, there may be an issue with the boiler’s internal gas valve.
4. Blocked or Dirty Pilot Light Jet
A small amount of debris or residue can block the tiny aperture of the pilot light jet, reducing the flame to the point where it struggles to stay lit. This is more common in older boilers that haven’t been serviced recently.
Cleaning the pilot light jet requires the boiler to be isolated from the gas supply first. This isn’t a job to attempt without the right tools and training.
5. Problem with the Gas Valve
The gas valve controls the flow of gas to both the pilot and main burner. If it develops a fault — which can happen with age or wear — it may intermittently cut the gas supply, causing the pilot light to go out without warning.
A faulty gas valve typically requires replacement rather than repair. This is a job for a Gas Safe registered engineer only.
6. Weak or Misaligned Pilot Flame
Sometimes the pilot flame itself is too small or positioned incorrectly relative to the thermocouple. If the tip of the thermocouple isn’t sitting properly within the flame, it won’t register that the flame is burning and will shut off the gas.
This can happen after a service if components weren’t repositioned correctly, or simply through gradual movement over time.
Why Relighting a Pilot Light Isn’t a DIY Job
You may see guides online that walk through relighting a pilot light yourself with a match or the boiler’s ignition button. We’d rather be straightforward with you: the pilot sits right at the gas components inside the boiler, and under Gas Safe regulations, only a Gas Safe registered engineer should be working on or around a gas appliance’s ignition system — including relighting a pilot that keeps failing.
A pilot that won’t stay lit on its own is telling you something’s wrong — most often a worn thermocouple, a gas supply issue, or a fault with the gas valve. Relighting it repeatedly doesn’t fix any of those, and handling the gas components yourself carries real risk if something isn’t seated correctly afterwards.
What If My Pilot Light Keeps Going Out?
A pilot light that goes out once might just be a one-off draught. But if it keeps happening, that’s a sign of an underlying fault — a worn thermocouple, a gas supply issue, or a failing gas valve — and none of those are things to keep working around yourself.
Rather than repeatedly relighting it, book a Gas Safe registered engineer to diagnose the cause. It’s usually a fast, low-cost fix once identified, and it removes the guesswork — and the risk — of doing it yourself.
When Is It an Emergency?
A pilot light going out is frustrating but not always a crisis. However, treat it as an emergency if:
- You can smell gas anywhere in your home
- The boiler is making unusual sounds alongside the fault
- There’s any sign of scorching, leaking, or discolouration around the boiler
- Vulnerable people in the home rely on the heating (elderly, very young children, people with health conditions)
In these situations, don’t delay. Heat365 offers 24/7 emergency plumbing and heating support across Sheffield, Rotherham, Chesterfield, Barnsley, Doncaster and Worksop.
Does My Boiler Need Servicing?
If your pilot light is causing recurring problems, it’s a strong indicator that your boiler is due a service — or overdue one. Annual boiler servicing helps catch small issues like a deteriorating thermocouple, dirty jet, or misaligned components before they become full breakdowns.
Gas Safe regulations don’t require homeowners to service their boilers annually, but most boiler manufacturers recommend it, and it typically keeps warranties valid.
A service from a Gas Safe registered engineer includes checking the pilot assembly, thermocouple condition, gas pressure, and overall safety — exactly the checks that prevent problems like this recurring.
Could It Be Time for a New Boiler?
Pilot light faults are common in older boilers. If yours is more than 15 years old and the same fault keeps returning, it’s worth considering whether a replacement makes more financial sense than repeated repair bills.
A modern condensing boiler uses electronic ignition rather than a standing pilot light, which removes this type of fault entirely. It also runs significantly more efficiently, which reduces ongoing energy costs.
If you’re unsure whether repair or replacement is the better route, a heating engineer can give you an honest assessment based on the age, condition, and fault history of your current boiler. For full details on what’s involved, visit our boiler installation Sheffield page.
| Fault Symptom | Likely Cause | DIY or Engineer? |
|---|---|---|
| Pilot lights but goes out when button released | Faulty thermocouple | Engineer |
| Pilot goes out in windy or cold conditions | Draught around boiler | Check seals — Engineer if persistent |
| Pilot won’t light at all | Gas supply or gas valve issue | Engineer |
| Pilot flame weak or flickering | Blocked jet or low gas pressure | Engineer |
| Pilot lights then goes out after a few minutes | Thermocouple or gas valve | Engineer |
Boiler Pilot Light FAQs
Is it safe to leave a boiler with a pilot light that keeps going out?
If the boiler shuts itself off, it’s doing what it’s supposed to. The risk is more practical than safety-critical — no heat or hot water — unless you’re smelling gas, in which case treat it as an emergency immediately.
How long does a thermocouple replacement take?
For an experienced heating engineer, a thermocouple replacement typically takes less than an hour. It’s one of the simpler boiler repairs, though it must be carried out by a Gas Safe registered engineer.
How much does it cost to fix a pilot light on a boiler?
A thermocouple replacement is usually one of the more affordable boiler repairs. The exact cost depends on your boiler make and model, and the engineer’s call-out charge. Get in touch with Heat365 for a clear, upfront quote.
Can I use my boiler without the pilot light?
No. Without the pilot light (or the electronic ignition equivalent), the main burner can’t be activated. The boiler simply won’t start until the ignition issue is resolved.
Boiler Pilot Light Problem? Call Heat365
Gas Safe registered engineers covering Sheffield and surrounding areas. Available 24/7 for heating emergencies — and for straightforward repairs too.
If your pilot light keeps going out, don’t keep relighting it yourself. A Gas Safe engineer can diagnose the fault quickly, carry out the repair safely, and get your heating working again. Contact Heat365 on 07534 793949 or email info@heat365.co.uk.
