Why Is My Boiler Clicking and Not Igniting? 4 Causes and Fixes in West London

A boiler that clicks away without ever catching flame is unsettling to hear. It sounds like it’s trying and failing.

What’s actually clicking behind the casing

Every gas boiler goes through the same short sequence on start-up. Understand it and the clicking sounds less alarming.

Your room thermostat calls for heat. The fan spins up first. It purges any leftover gas from the flue. Once the air pressure switch confirms a good draught, the ignition generator pulses high-voltage current across the spark electrodes. That’s the ticking sound you hear, roughly a dozen sparks a second, each one jumping a gap of about 3 to 4mm.

If the spark looks right, the gas valve opens and the burner should light. A flame sensing probe checks next. It confirms a genuine flame is present. If it is, the sparking stops and the burner just runs. If any one step fails, the whole sequence aborts and tries again. That’s why you hear clicking in short repeated bursts, not one long spark.

The 4 reasons your boiler clicks but won’t fire

Here’s how the four failure points stack up, based on what our engineers see most.

On the jobs our engineers attend, worn or sooted spark electrodes are by far the most common of the four. A seized gas valve or low working gas pressure does happen too. But it’s the less frequent finding once the boiler is opened up.

There’s a simple way to tell what’s clicking before an engineer even arrives. Fan relays barely click at all. So that’s rarely the culprit. If the clicking is coming from inside the boiler itself, it’s almost certainly the spark igniter. If it’s coming from an airing cupboard, or wherever your motorised zone valve sits, that’s a separate fault with a different fix.

Why this shows up more as the heating season starts

Clicking faults spike in October and November. There’s a reason for that. A boiler that’s sat mostly idle through summer, running only for the odd hot water demand, gets asked to fire far more often once the heating comes back on every day. Worn electrodes that coped fine with occasional use suddenly can’t hold a reliable arc under daily cycling.

Check your warranty position first. Most manufacturer warranties are void the moment anyone other than a Gas Safe registered engineer opens the casing, even for a quick look. If your boiler is still within its warranty period, tell us the model and age when you call. We’ll confirm whether the fault is covered before any chargeable work goes ahead.

An annual service catches worn electrodes and drifting spark gaps before they turn into a lockout on the coldest morning of the year. Our boiler servicing checks combustion settings, electrode condition and flame signal strength as standard, which is exactly the sort of small, unglamorous check that prevents this exact call-out.

Safe checks you can do yourself vs Gas Safe limits

A few checks are safe without any tools. Others cross a legal line the moment you touch them.

What you can safely check:

1. Test your gas supply. Turn on a hob burner. If it lights, gas is reaching your home. The fault sits inside the boiler.
2. Check a prepayment meter. Confirm there’s credit and that emergency credit hasn’t already run out. A dry meter looks exactly like a boiler fault from the airing cupboard.
3. Try one clean reset. Hold the button for 3 to 5 seconds. Then wait. Give it a fair chance to complete its sequence before deciding it hasn’t worked.

What needs a Gas Safe engineer:

• Taking the front casing off to look at the burner or electrodes. It’s against the law without Gas Safe registration.
• Adjusting the gas valve, measuring inlet working pressure, or touching anything behind the panel.
• Cleaning or realigning the spark electrodes yourself. The gap has to sit at a precise 3 to 4mm.

Don’t keep pressing reset if the first attempt fails. Each attempt pushes a little unburnt gas into the chamber. Repeat that enough times and the chamber floods with gas. On the next spark, that gas can ignite all at once rather than in a controlled burn. That can damage the heat exchanger. One reset, then stop.

What it costs to fix

Our diagnostic fee is fixed for the time window you book, whatever the fault turns out to be. Any parts or repair work is quoted in writing first.

Once we’ve confirmed the fault, parts typically fall into these ranges, on top of the diagnostic fee.

• Spark electrodes and ignition lead cost around £100 to £180 supplied and fitted.
• Flame rectification sensor replacement costs around £110 to £170 supplied and fitted.
• Combustion fan assembly replacement costs around £220 to £360 supplied and fitted.
• Gas valve replacement, including supply, fit and a combustion recalibration, costs around £260 to £420.

These are typical ranges, not a quote. You’ll always get a fixed price agreed in writing before any repair goes ahead. Our Homeowner Plan at £9.99 a month includes an annual service that checks electrode condition and combustion settings before they turn into a breakdown.

What our engineer does on the visit

1. Checks the fault history. Asks what you’ve already tried and how many times reset has been pressed.
2. Confirms gas supply and working pressure at the meter with a calibrated digital manometer.
3. Removes the front casing to inspect the spark electrodes. Checks the gap and condition.
4. Tests the flame rectification signal through a full burn cycle.
5. Checks fan operation and air pressure switch response during the pre-purge stage.
6. Agrees a fixed price before starting any repair.

Boiler clicking or something else?

A few other faults sound similar from the airing cupboard. It’s worth ruling them out.

• A motorised zone valve clicks from its own location, usually a cupboard or loft, not from inside the boiler casing itself.
• No clicking at all, and a completely dead boiler, points to an electrical fault, most likely a tripped fuse spur, rather than an ignition problem.
• Firing normally but locking out later in a heating cycle is a different fault, often linked to a fault code rather than the ignition sequence itself.

Not sure which one you’ve got? Our emergency boiler repair team can talk you through it over the phone before booking a visit. Our checklist for a boiler breaking down in winter covers the wider pre-call triage.

Need a Gas Safe engineer for a boiler that’s clicking and won’t ignite?

Tell us the sound it’s making, whether it fires briefly before cutting out, and what you’ve already tried. We’ll get an engineer to you with a clear fixed price agreed before any work starts.

• WhatsApp: Book in 60 seconds
• Call: 020 8051 2124, answered 24/7
• Book online: boiler repairs · boiler installation for boilers beyond economical repair

We’re Gas Safe registered (657972). We cover West and North West London, including Kensal Rise, Queen’s Park, Kilburn, Acton, Ealing and Fulham. Heating that just works, no drama.

Frequently asked questions

Why is my boiler clicking repeatedly?

The spark generator is firing but the ignition sequence isn’t completing. Gas usually isn’t reaching the burner, the spark is too weak, or airflow hasn’t been confirmed by the fan and pressure switch. Worn spark electrodes are the most common cause we find on real jobs.

Is a clicking boiler dangerous?

Modern boilers have built-in safety cutouts. A clicking boiler that keeps locking out is designed to stop rather than run unsafely. The risk comes from what you do next. Repeatedly pressing reset can flood the combustion chamber with unburnt gas. Turn the boiler off at the fused spur and book a Gas Safe engineer instead.

Why does my boiler fire for 2 seconds then click again and shut down?

That pattern points to a faulty flame rectification sensor. The burner lights briefly. But the sensing probe is sooted, cracked or has lost its connection, so it can’t confirm a genuine flame. The control board plays it safe and cuts the gas.

Can I fix a clicking boiler myself?

You can check your gas supply on a hob burner, confirm a prepayment meter has credit, and try one clean reset. Anything past that has to be done by a Gas Safe registered engineer. That includes the casing, the electrodes, the gas valve and any combustion seals. It’s a legal requirement, not just good practice.

How do I tell if it’s the spark igniter clicking or something else?

Fan relays barely click. If the clicking is coming from inside the boiler casing, it’s almost certainly the spark igniter trying to fire. If the sound is coming from an airing cupboard, or wherever a motorised zone valve is fitted, that’s a separate fault with a different fix.

Why shouldn’t I keep pressing the reset button?

Every failed attempt pushes a small amount of gas into the combustion chamber that doesn’t burn off. Reset it enough times and that gas builds up. On the next spark, it can ignite all at once rather than in a controlled burn. That risks damaging the heat exchanger or burner. Press it once, then call an engineer if it hasn’t worked.

How much does it cost to fix a clicking boiler in West London?

Our fixed weekday daytime diagnostic fee is £120. That rises to £160 on Saturdays, £180 for evening visits, and £220 for emergency dispatch on a Sunday or Bank Holiday. Once the exact cause is confirmed, typical repairs range from around £100 for spark electrodes up to £420 for a gas valve replacement, always quoted in writing before we start.