Boiler Not Igniting (Clicks But No Flame)
If your boiler is clicking repeatedly but no flame appears, the boiler is trying to ignite and failing. This is different from a boiler that is completely dead or not responding at all.
Clicking usually means:
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The boiler has power
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The ignition sequence is starting
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A safety condition is preventing the flame from establishing
Modern boilers are designed to abort ignition safely if anything isn’t quite right. The clicking you hear is the boiler making repeated ignition attempts before locking itself out.
What the clicking sound actually means
When a boiler starts, it follows a strict ignition sequence:
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System checks (pressure, sensors, safety switches)
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Fan runs to clear the combustion chamber
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Gas valve opens
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Ignition electrode sparks
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Flame should establish and be detected
If any step fails, the boiler will stop, pause, and try again.
Clicking with no flame means:
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The spark is happening
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But the flame is not forming or not being recognised
Common reasons a boiler clicks but won’t ignite
1. Gas supply issue (most common)
Even if other gas appliances work, the boiler may not be receiving stable gas flow.
This can happen due to:
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Recently disturbed gas supply
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Low inlet pressure
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Partially closed isolation valve
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Air in the gas line after work or outage
The boiler may spark, but without consistent gas flow, the flame cannot establish.
2. Ignition electrode or lead fault
The ignition electrode creates the spark that lights the gas.
Problems we regularly see:
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Worn or cracked electrode
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Poor positioning
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Insulation breakdown on the ignition lead
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Weak spark that looks fine but won’t light reliably
This often causes repeated clicking with no flame and no obvious error code.
3. Flame sensor not detecting the flame
Sometimes the flame does light briefly, but the boiler shuts it down immediately.
Why?
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The flame sensor doesn’t “see” the flame
Common causes:
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Dirty or oxidised flame sensor
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Poor earthing
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Sensor wiring fault
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Weak flame due to gas or burner issues
To the boiler, no flame detected = unsafe → gas shut off.
4. Low boiler pressure or system safety lockout
If system pressure is too low, the boiler may:
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Start ignition
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Abort before allowing the flame
This often happens when pressure is borderline, not fully empty.
You may still hear clicking, but the boiler won’t commit to ignition.
5. Condensate or flue safety interruption
Modern boilers monitor flue and condensate conditions closely.
Ignition may fail if:
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Condensate pipe is frozen or restricted
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Internal condensate trap is partially blocked
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Flue pressure switch isn’t proving airflow correctly
The boiler may attempt ignition but stop as soon as safety checks fail.
6. Gas valve or control fault
Less common, but serious when it occurs.
Examples:
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Gas valve opening intermittently
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Control board not sending correct signals
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Internal relay faults
These usually present as intermittent ignition failure, often worse when cold.
Why repeated resets are a bad idea
Many homeowners instinctively keep resetting the boiler.
This can:
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Flood the combustion chamber with unburned gas
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Overheat ignition components
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Turn a small fault into a lockout or damaged part
If the boiler clicks several times and fails:
Stop resetting it.
The boiler is protecting itself.
When this becomes urgent
Call for professional help immediately if:
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You smell gas
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The boiler locks out repeatedly
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The boiler ignites briefly then shuts down
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Clicking continues for long periods
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The issue appeared suddenly after other work
Ignition faults are not DIY issues.
What an engineer will check
A proper ignition diagnosis includes:
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Gas inlet pressure testing
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Ignition electrode inspection
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Flame signal testing
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Condensate and flue checks
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Control sequence verification
Guessing or swapping parts blindly often makes things worse.
What to do next
If your boiler is clicking but not igniting:
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Avoid repeated resets
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Note any error codes
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Check pressure visually (don’t adjust yet)
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Arrange a professional inspection
A clicking boiler is usually very close to working, but something is stopping it safely.
If your boiler still won’t ignite, it’s time for a full system diagnosis.
Further help
If this issue is part of a wider problem, see the main guide:
Boiler Not Working / Won’t Fire Guide →
If the boiler still won’t ignite, a proper repair is the safest route.
A Gas Safe engineer can diagnose ignition faults accurately without unnecessary parts or risk.