- Boilers
- Gas boiler
E129
Baxi E129 on a gas boiler: flame loss during ignition
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
Baxi E129 means flame loss during ignition: the burner lights but the flame does not hold. Baxi gives no user reset for 129: it says to call the authorised technical service. Check that the yellow gas tap is open.
Safety first
Stop and check this first
- If you smell gas: Baxi says to switch the boiler off, not to operate any electrical device or switch on lights, to put out any flame and open the windows. Then leave the home and call your gas distributor's emergency number and the service centre from outside.
- If you smell combustion fumes: Baxi says to switch the boiler off, ventilate by opening doors and windows and call the service centre. Carbon monoxide has no smell; if anyone has a headache, dizziness or nausea, get outside and seek help. A CO alarm near the boiler gives early warning.
Safe checks you can perform
- Gas smell, combustion smell or symptoms
- Gas tap open
- Flue terminal seen from outside
- Inspection by the technician
Leave these tasks to a qualified professional
- Do not attempt this professional task: Detection electrode and its position
- Do not attempt this professional task: Ionisation current and wiring
- Do not attempt this professional task: Flue and combustion analysis
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Detection electrode and its position
What they doThe technician checks the electrode condition and its position following the electrode positioning section of the manual.
They must show youthe electrode and its position, with a photo.
In writingif it was replaced, the part number and why.
Ionisation current and wiring
What they doThe technician checks cable continuity and contact with the electrode and igniter, and measures the ionisation current with the flame lit.
They must show youthe value measured against the manufacturer's specification.
In writingthe fault found.
Flue and combustion analysis
What they doThe technician looks for flue gas recirculation in the flue and terminal and measures combustion with an analyser.
They must show youthe analyser printout.
In writingthe values measured against the manufacturer's and what was corrected in the flue.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Gas smell, combustion smell or symptoms
- Who:
- you.
- How:
- first, notice whether there is a smell of gas or burnt gases near the boiler, or whether anyone has a headache, dizziness or nausea.
- Result that matters:
- whether there are signs of gas or fumes indoors.
- If you smell gas:
- follow the gas warning: leave the home and call from outside.
- If you smell combustion fumes:
- switch the boiler off, ventilate and call the service centre, as Baxi asks.
- Evidence to keep:
- a note of the time and what you noticed.
Evidence: Baxi Neodens Plus 24/24 F ECO, 28/28 F ECO y 33/33 F ECO, instrucciones de funcionamiento y mantenimiento para el usuario 7731457
Gas tap open
- Who:
- you.
- How:
- check that the gas tap, yellow and located under the boiler, is open, as Baxi asks for start-up. Do not touch other valves or pipes.
- Result that matters:
- whether gas reaches the boiler.
- If it was closed:
- open it and still tell the technician about the code.
- If it was open:
- the problem is in flame detection or the flue.
- Evidence to keep:
- photo of the tap.
Evidence: Baxi Neodens Plus 24/24 F ECO, 28/28 F ECO y 33/33 F ECO, instrucciones de funcionamiento y mantenimiento para el usuario 7731457
Flue terminal seen from outside
- Who:
- you.
- How:
- look at the flue terminal from the ground or a window, without touching it or climbing.
- Result that matters:
- whether it is blocked, damaged or next to something that sends the fumes back to the air intake.
- If something looks wrong:
- tell the technician; it may fit flue gas recirculation.
- If it looks clear:
- it points more to the electrode or its cable.
- Evidence to keep:
- photos of the terminal.
Evidence: Baxi Neodens Plus 24/24 F ECO, 28/28 F ECO y 33/33 F ECO, instrucciones de instalación, montaje y funcionamiento para el instalador 7731458
Inspection by the technician
- Who:
- Baxi authorised technical service.
- How:
- checks the detection electrode, its cable and contact, and checks for flue gas recirculation.
- Result that matters:
- which part prevents the flame from holding.
- If the electrode is damaged or out of position:
- it is repositioned or replaced as the manual describes.
- If there is recirculation:
- the flue is corrected before the boiler is lit again.
- Evidence to keep:
- job sheet with what was checked and the parts replaced.
Electrodes, burner, gas valve and flue are technician-only work. Baxi gives no user reset for 129.
Evidence: Baxi Neodens Plus 24/24 F ECO, 28/28 F ECO y 33/33 F ECO, instrucciones de instalación, montaje y funcionamiento para el instalador 7731458
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Boilers
- Brand
- Baxi
- Product type
- Gas boiler
Known code variants
- 129
- Baxi 129
- Baxi E 129
- Error 129 Baxi
- Neodens Plus 129
What it means
On the Neodens Plus ECO, code 129 is flame loss during ignition. For the user, Baxi says to call the authorised service centre. In the installer manual it says to check the condition and position of the detection electrode, cable continuity and contact with the detection electrode and the igniter, and any flue gas recirculation. The code does not say which of these is at fault: it may be the electrode, its cable or flue gases coming back in.
Warnings and stop conditions
- Criticaleditorial warning
If you smell gas: Baxi says to switch the boiler off, not to operate any electrical device or switch on lights, to put out any flame and open the windows. Then leave the home and call your gas distributor's emergency number and the service centre from outside.
Evidence: Baxi Neodens Plus 24/24 F ECO, 28/28 F ECO y 33/33 F ECO, instrucciones de funcionamiento y mantenimiento para el usuario 7731457
- Higheditorial warning
If you smell combustion fumes: Baxi says to switch the boiler off, ventilate by opening doors and windows and call the service centre. Carbon monoxide has no smell; if anyone has a headache, dizziness or nausea, get outside and seek help. A CO alarm near the boiler gives early warning.
Evidence: Baxi Neodens Plus 24/24 F ECO, 28/28 F ECO y 33/33 F ECO, instrucciones de funcionamiento y mantenimiento para el usuario 7731457
Symptoms and causes
Probable causes · in order
- Detection electrode damaged or out of positionPossible
Baxi says to check its condition and position. If the electrode does not sense the flame properly, the boiler treats it as lost.
Evidence: Baxi Neodens Plus 24/24 F ECO, 28/28 F ECO y 33/33 F ECO, instrucciones de instalación, montaje y funcionamiento para el instalador 7731458
- Electrode cable or contactPossible
Baxi says to check cable continuity and contact with the detection electrode and igniter. A poor contact cuts the flame signal.
Evidence: Baxi Neodens Plus 24/24 F ECO, 28/28 F ECO y 33/33 F ECO, instrucciones de instalación, montaje y funcionamiento para el instalador 7731458
- Flue gas recirculationPossible
Baxi says to check for flue gas recirculation. If the exhaust gases come back into the air intake, the flame does not hold.
Evidence: Baxi Neodens Plus 24/24 F ECO, 28/28 F ECO y 33/33 F ECO, instrucciones de instalación, montaje y funcionamiento para el instalador 7731458
Virtual technician
Does E129 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
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