False Flame Lockout
The L6 error code on Ideal boilers indicates false flame lockout.
Ideal L6 means: false flame lockout. On this component the documented failure modes are ignition or detection electrode dirty, worn or out of position or wiring, connector or harness of the false flame damaged or loose. A Gas Safe registered engineer should diagnose the root cause.
What Does L6 Mean
The L6 code is shown by the boiler’s control board when it detects false flame lockout. The boiler then stops instead of continuing to run in that condition: the code is the appliance reporting a problem, not proof that the boiler is broken.
| What you see on the boiler |
|---|
| The display shows L6 and the boiler stops until the fault is cleared |
Common Causes
The manufacturer does not publish a cause list for this specific code. The causes below are the failure modes documented for the same component on other boilers, confirmed by the service literature of 4 different manufacturers.
| Cause |
|---|
| Ignition or detection electrode dirty, worn or out of position |
| Wiring, connector or harness of the false flame damaged or loose |
Safety Warning
L6 is a gas-related fault. Never attempt to repair or adjust the gas valve, burner assembly, or flue system yourself. All gas work must be carried out by a Gas Safe registered engineer (UK) or licensed HVAC technician (US). Repeated resets after ignition failure can cause unburnt gas to accumulate inside the combustion chamber — this is a serious safety hazard. If you smell gas at any point, turn off the gas supply at the meter, open windows, leave the property, and call your gas emergency service immediately. Gas-related fault. Do not open the boiler casing or attempt repairs to the gas valve, burner, ignition or flue. Repeated resets are unsafe. Diagnosis and repair must be carried out by a Gas Safe registered engineer.
Parts & Prices
Prices shown are indicative. Actual prices and availability vary by region.
Step-by-Step Diagnosis
1. Verify gas supply — check gas meter is on and other gas appliances work. 2. Inspect the ignition electrode — look for cracks, carbon build-up, or incorrect gap (typically 3-4mm). 3. Check the ignition lead — ensure it is securely connected and not damaged. 4. Test the gas valve — measure voltage at the gas valve terminals during ignition attempt (should read 24V AC or mains depending on model). 5. Inspect the flue system — check for blockages, birds' nests, or debris. 6. Check the condensate trap and drain — a blocked condensate pipe can prevent ignition. 7. Verify the ionisation probe is clean and correctly positioned. 8. If all above pass, test the PCB by measuring outputs during ignition sequence
How to Fix It
Inspect the ignition and detection electrode: clean off any deposits, check the gap and position against the manual, and replace it if it is worn.
Unplug and re-seat the connector of the false flame, then check the harness for chafing, corroded pins and breaks in continuity.
Refer to the Ideal service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
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Affected Models
Ideal models that can display fault code L6:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Ideal models | — | Possible |
Frequently Asked Questions
Inspect the ignition and detection electrode: clean off any deposits, check the gap and position against the manual, and replace it if it is worn. According to the technical documentation, this is the first check on the list for L6.
L6 is classified as a high-severity fault: it involves gas, combustion or flue components. Do not keep resetting the boiler and do not attempt the repair yourself — call a Gas Safe registered engineer.