Ideal L6 fault code: false flame explained

What does the Ideal L6 fault code mean?

L6 is a false-flame lockout. Your boiler has a flame-detection electrode inside the combustion chamber whose job is to confirm a flame is present when the boiler is firing, and to confirm there is no flame when the gas valve is closed. L6 appears when the control board is told a flame is present at a moment when there should not be one: no heating or hot water demand is active, and the gas valve should be sealed shut. The boiler locks itself out immediately rather than carry on.

This is one of the fault codes where the honest advice is to lean towards calling an engineer sooner rather than trying much yourself. The reason is that L6 sits right on the boiler's gas and flame-sensing safety system: either the electrode is misreading, or gas really is reaching the burner when it should not be, and only a Gas Safe registered engineer can tell which. The safe checks below are deliberately short for exactly that reason.

The lockout is the safety system doing its job. But if you ever smell gas or your carbon monoxide alarm sounds, that is a separate emergency whatever code is on the screen. Call the National Gas Emergency Service on 0800 111 999 straight away.

Key facts

The quick version, before the detail.

• What it means: a false flame. The boiler senses a flame while the gas valve should be closed, so it locks out.
• DIY-fixable? Barely: one reset or power cycle, and a quick check that other gas appliances work. That is all.
• Gas Safe job if: L6 returns after one reset, which it usually does, because the flame electrode, gas valve or control board needs testing.
• Why it matters: L6 is on the gas and flame-sensing safety system, so it is not one to keep resetting.
• Smart Plan boiler cover: parts and labour included up to £500 a year (boiler under 7 years) or up to £200 a year (over 7 years).
• Call-outs are Monday to Friday, 08:00 to 18:00; a £95 call-out fee, paid in advance, applies in your first 30 days, for faults the plan does not cover, if the engineer cannot get access, and for early annual-service requests.

Why does the Ideal L6 code appear?

Because L6 is about the boiler sensing a flame at the wrong moment, the causes cluster around the flame-detection and gas-supply parts rather than around pressure or radiators. The most common cause by far is a faulty flame-detection electrode reporting a flame that is not really there. Next is a gas valve that is sticking or leaking slightly, so a small amount of gas or flame is present when the valve should be sealed. Less often, the control board itself misreads the signal or generates a false reading internally.

The table below lists these roughly most-likely first. What they share is that every one of them is engineer work: none of them is safe to check or fix from outside the boiler.

Ideal L6 causes and symptoms

Can I fix the Ideal L6 code myself?

There is very little to do safely at home with L6, and that is the honest answer rather than a short one for its own sake. Because the code sits on the gas valve and flame-sensing safety system, the only steps that are yours to take are these, and you should not go beyond them.

1. Reset the boiler once, using the reset button or by turning the power off and on at the fuse spur. Do this once only.

2. Check that your other gas appliances are working normally, which helps an engineer rule the wider gas supply in or out before they arrive.

That is the full list. Do not open the boiler casing, and do not touch the electrode, gas valve or control board: all of those are Gas Safe registered engineer work. If L6 comes straight back after one reset, which it usually does, stop resetting and book an engineer rather than override a gas-safety lockout again and again.

When to call a Gas Safe registered engineer

With L6, that point comes quickly. If one reset does not clear it, book an engineer, and do not keep resetting in the meantime. Because the fault is on the flame-sensing and gas-valve safety system, an engineer will test the flame-detection electrode, check the gas valve for sticking or leaking, and check the control board, then fix the actual cause. That diagnosis is not something that can be done safely from outside the boiler, which is why L6 is more of a call-an-engineer code than most. You can check an engineer's registration on the Gas Safe Register.

Covering a fault like this with Smart Plan

Smart Plan is a service plan, not insurance. If you would rather not face a surprise repair bill next time L6 shows up, an ongoing boiler module covers parts and labour up to your cover limit. Cover is modular: you build your own plan and pick only what you want, and older Ideal boilers are welcome. Boiler cover runs up to £500 a year if your boiler is under 7 years old, or up to £200 if it is older. A £95 call-out fee, paid in advance, applies in your first 30 days, for faults the plan does not cover, if the engineer cannot get access, and for early annual-service requests. Cover-plan call-outs run Monday to Friday, 08:00 to 18:00. Outside those hours you are only seen sooner for a genuine emergency breakdown, so a fault outside those hours can wait until the next working day. Using a module starts a 12-month agreement period the first time you use a service; there is a 14-day cooling-off period, but it ends once a service is carried out, and leaving early after that costs the remaining months or 75% of the outstanding balance. Prefer to deal with it right now? You can book a one-off repair instead and a Gas Safe registered engineer will come and fix it for you.

We have looked after over 15,000 customers, and we are from UK Boiler Company Ltd, trading since 2014. Call 0333 772 6247 (Monday to Friday, 08:00 to 18:00) to talk it through, or build your plan online.

Safe checks before you call anyone out

There is only a little you can safely do with an Ideal L6 fault. If it does not clear, the next step is a Gas Safe registered engineer.

• Reset the boiler once at the reset button or the fuse spur. Do not keep resetting if L6 comes back.
• Check that other gas appliances in the home are working normally.
• Never open the boiler casing or touch the flame electrode, gas valve or control board: that is a Gas Safe registered engineer's job.
• Do not keep overriding L6. It is a gas-safety lockout, so a recurring L6 is an engineer job, not a reset job.
• If you ever smell gas or your CO alarm sounds, stop. Call 0800 111 999, open windows, turn off the gas at the meter, do not touch electrical switches, and leave the house.

Ideal L6 fault code FAQs

Seeing L6 on your Ideal boiler? We'll come and fix it for you.

Book a one-off repair and a Gas Safe registered engineer will test the flame electrode and gas valve and fix the cause, or set up an ongoing Smart Plan boiler module so the next fault is covered. A service plan, not insurance: parts and labour included up to your cover limit.

Helpful links

• Ideal L2 flame-loss fault code
• Ideal F2 flame-loss fault code
• All Ideal fault codes
• Ideal L1 fault code
• Ideal boiler help and guides
• Boiler repair
• Boiler & central heating cover
• Check an engineer on the Gas Safe Register