Boiler fires up but there is no flame: what now?

A boiler can start its fan or pump, make an ignition sound and light up its display without ever establishing a burner flame. If the flame is not safely proved, the boiler should stop the ignition attempt and may lock out. That safety response is preferable to allowing unburned gas to continue flowing.

This guide explains the safe checks a homeowner can make, what common Baxi, Worcester Bosch, Ideal, Vaillant and Viessmann messages mean, and when to stop resetting and arrange a qualified repair. It does not involve removing the boiler case or attempting work on gas, combustion or ignition components.

First: what does “fires up but no flame” mean?

People often say a boiler “fires up” when they hear the fan, pump, clicks or other starting noises. Those signs only show that part of the start sequence is happening. A modern gas boiler normally checks several conditions, starts its fan, attempts ignition and then looks for a reliable flame signal. If that flame is not detected, or it appears and then disappears, the controls shut the attempt down.

The distinction matters. A boiler that is simply in standby has not necessarily tried to ignite. A boiler that repeatedly clicks, runs its fan and then shows a lockout has tried and failed. Record the exact sequence, display message and fault code rather than trying to diagnose the internal part yourself.

Gas smell or carbon monoxide alarm? Treat it as an emergency

If you smell gas, suspect a gas escape or a carbon monoxide alarm sounds, do not reset the boiler or operate electrical switches. Open doors and windows, turn off the gas at the meter if you can do so safely, leave the affected area and call the National Gas Emergency Service on 0800 111 999. Follow the operator’s instructions.

Carbon monoxide cannot be seen, tasted or smelled. Headache, dizziness, nausea, breathlessness, collapse or confusion can be symptoms of exposure. Get into fresh air, seek urgent medical advice and do not use the appliance again until it has been checked by a competent Gas Safe registered engineer.

Safe checks before booking a repair

1. Record the model and exact code

Take a photograph of the display and write down the boiler’s full model name. Similar-looking codes can mean different things: for example, Ideal’s current Logic user guidance identifies F1 as low water pressure, while F2 relates to flame loss and L2 to ignition lockout. Do not assume every “F” code is an ignition fault.

2. Confirm there is a genuine demand

Set the thermostat above the measured room temperature and check that the programmer is in an active heating period. For a combi boiler, you can also note whether opening a hot tap creates a separate demand. If the boiler stays completely silent, the issue may be controls, power or demand rather than failed ignition.

3. Check power without opening anything

Confirm the display is lit and that an obvious wall switch has not been turned off. Check the consumer unit only as you would for any normal household circuit. Do not remove fused-spur covers, replace internal fuses or work on boiler wiring.

4. Check whether the property has gas

Only if there is no smell of gas, check whether another gas appliance works and whether a prepayment meter has credit. A wider supply interruption can prevent ignition. Do not keep trying the boiler if other gas appliances also fail; contact the gas supplier or follow the meter provider’s guidance.

5. Read the pressure from outside the boiler

Some boilers will not operate when sealed-system pressure is outside the permitted range. Compare the gauge or display with the exact user manual. Only repressurise if that manual gives a homeowner procedure and you are confident using the fitted controls. Low pressure is not the same as no flame, and repeatedly topping up a system that loses pressure can conceal a leak.

6. In freezing weather, inspect the external condensate pipe

A frozen condensate pipe can stop some boilers and can appear alongside an ignition or condensate-related lockout. If the manufacturer’s homeowner instructions identify a safely accessible external section, it may be thawed with warm—not boiling—water. Do not climb, dismantle pipework or work where the surface is slippery. If you are unsure, call an engineer.

7. Try one manufacturer-approved reset

Use the normal user reset control only when the exact boiler manual instructs you to. Give the boiler time to complete its sequence. If the same lockout returns, stop. Repeated resetting does not repair a failed ignition or flame-sensing system and can obscure the pattern that helps an engineer diagnose it.

Why a boiler may not establish a flame

The display cannot tell a homeowner which component has failed. It reports the condition detected by the boiler’s controls. The underlying cause can sit in several different areas:

• Gas supply: an interrupted supply, closed control, meter issue or inadequate inlet condition.
• Ignition: a problem with the spark generator, ignition electrode, lead or their positioning.
• Flame detection: a flame may light but not be reliably proved by the sensing system.
• Gas valve or controls: the valve, wiring or control board may not operate as required.
• Air or flue: the boiler may prevent operation when safe combustion or flue conditions cannot be confirmed.
• Condensate: a blockage or frozen external pipe can stop a condensing boiler.
• Combustion components: contamination, wear or incorrect combustion conditions may require testing and servicing.

Those are professional diagnostic categories, not a DIY checklist. Testing ignition, gas pressures, gas valves, flame signals and combustion requires the correct instruments, manufacturer information and competence. The boiler case must remain closed.

What common manufacturer codes mean

Baxi E133

Baxi describes E133 as a gas supply fault. Its technical support information also lists professional checks involving the sensing electrode, spark electrode and ignition lead. Baxi’s frozen-condensate guidance notes that some boilers may show E133 when condensate is frozen. A homeowner can check the property supply, meter credit and an accessible external condensate pipe, but internal diagnosis belongs to an engineer.

Worcester Bosch EA or 227

Worcester Bosch literature uses 227 for a flame signal not detected after ignition. Some displays combine this with EA. Manufacturer fault-finding information covers possible gas-supply, ignition, flame-sensing, condensate, air-intake, flue and burner causes. That breadth is why replacing a guessed part is not a sensible response to the code.

Ideal L2 and F2

Ideal’s Logic user guide identifies L2 as ignition lockout and F2 as flame loss. It advises checking other gas appliances and the gas meter or prepayment credit, and for L2 it includes a condensate blockage among the homeowner observations. If the recommended checks and reset do not restore operation, an engineer is required. Ideal F1, by contrast, is low water pressure on the model covered by that guide.

Vaillant F.28 and F.29

Vaillant describes F.28 as failure to detect a flame during ignition and F.29 as an unsuccessful restart after flame loss. Its homeowner guidance suggests checking whether other gas appliances work, whether a prepayment meter has credit and whether an external condensate pipe is frozen. Internal work must be carried out by a qualified professional.

Viessmann ignition lockout

Viessmann explains that modern boilers generally use electronic ignition and that a boiler which will not ignite may lock out. Safe observations include power, thermostat demand, system pressure and the wider gas supply. Fault codes and reset methods vary by model, so use the specific Viessmann operating instructions rather than a generic code list.

What the sounds can tell you

A click followed by silence can mean an ignition attempt occurred, but it does not identify the failed part. A fan that starts and stops suggests the sequence began but a required condition was not completed. A brief flame symbol that vanishes may indicate that a flame was not proved or was lost. A quiet boiler with no demand indication points in a different direction, such as controls or power.

Do not use sound alone to decide that an electrode, gas valve or control board needs replacing. Give the engineer the timing, noises, exact code and whether the issue affects heating, hot water or both.

Can low pressure cause an ignition lockout?

Low system pressure can stop certain boilers, but the resulting message is model-specific. It does not automatically mean there is a gas or ignition failure. Check the displayed pressure and the exact manual. If pressure repeatedly falls after being restored, arrange an inspection instead of continually refilling the system.

Should you keep pressing reset?

No. One reset performed exactly as the user manual describes is reasonable after basic external checks. If the fault returns, repeated attempts waste time and may make the history harder to interpret. A persistent no-flame or flame-loss lockout needs proper testing.

Does the boiler need replacing?

Not necessarily. A no-flame lockout is a symptom, not a verdict on the boiler. Repair may be straightforward once the actual cause is measured. Replacement becomes a wider decision involving age, condition, parts availability, repair history, efficiency and cost—not the presence of a single code. Ask for a diagnosis before making that decision.

What to tell the engineer

• the full make and model;
• the exact code and wording;
• whether the fan, pump or ignition clicking can be heard;
• whether the flame appears briefly or never appears;
• whether heating, hot water or both are affected;
• the system pressure;
• whether other gas appliances work; and
• whether the weather is freezing or the condensate pipe is exposed.

Gas work in the UK must be carried out by a Gas Safe registered engineer who is competent for the appliance and work involved. You can check an engineer and their qualifications on the Gas Safe Register website.

Frequently asked questions

Why does my boiler click but not light?

The clicking may be part of the ignition attempt, but gas supply, spark, flame detection, controls, condensate, air or flue conditions can all prevent a confirmed flame. The boiler needs testing rather than a guessed repair.

Can I light the boiler manually?

No. Modern room-sealed boilers use controlled electronic ignition. Do not remove the case, introduce a flame or try to bypass the ignition sequence.

Can a frozen condensate pipe cause this?

Yes, on some condensing boilers. Follow only the manufacturer’s safe homeowner thawing guidance for an accessible external pipe and never use boiling water.

Why does the flame appear and then go out?

The flame may not be proved reliably, or the boiler may detect another unsafe condition. That requires professional diagnosis of the combustion and control system.

Is it safe to leave the boiler locked out?

A locked-out boiler should not continue trying to run, but the home may become cold and hot water may be unavailable. Do not use unsafe heaters or cooking appliances for warmth. Arrange repair, especially where vulnerable occupants could be affected.

Related boiler-help guides

• Baxi E133 fault code explained
• Worcester Bosch 227 ignition fault
• Why does my boiler reset keep failing?
• How to recognise a frozen condensate pipe
• Boiler not firing: safe checks