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A06

Cointra A06 on a gas boiler: no flame after ignition

Verified with sources1 sourceReviewed Oct 4, 2026
Technician coming? See the 3 steps they must show you
Wall-mounted combi gas boiler installed in a home
Kai KemmannCC BY-SA 4.0Image source

Risk level

High

Professional inspection is recommended.

Urgency

High

Quick answer

Cointra A06 means there is no flame after the ignition phase. Look from outside to see if the flue terminal is blocked, press reset for one second and, if the boiler does not restart, stop resetting and call an authorised technician.

Safety first

Stop and check this first

  • If you smell gas, do not reset: do not touch switches or light flames, open windows, close the gas tap if it is within reach, leave and call your gas distributor's emergency number from outside. Cointra says to switch the boiler off when it fails and to have it repaired only by an authorised technician.
  • Cointra warns of a risk of asphyxia from escaping flue gases if the boiler runs with the siphon empty. If you get a headache, dizziness or nausea, switch the boiler off, ventilate, leave the home and get help. A CO alarm near the boiler warns earlier.
  • Do not chain resets with A06: if the boiler does not restart, Cointra says the fault must be fixed. Do not open the boiler or touch the electrode, burner, siphon or ducts.

Safe checks you can perform

  • Gas or flue gas smell before anything else
  • Flue terminal and condensate drain, from outside
  • One reset with the reset key
  • Electrode, burner, siphon and duct check by the technician

Leave these tasks to a qualified professional

  • Do not attempt this professional task: Siphon and duct check
  • Do not attempt this professional task: Ionisation electrode check
  • Do not attempt this professional task: Combustion check and calibration

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.

  1. Siphon and duct check

    What they doThe technician checks that the siphon is full of water and clear and that the air and flue ducts and terminal have no blockages or leaks.

    They must show youthe siphon and terminal checked.

    In writingwhat was cleaned or corrected.

  2. Ionisation electrode check

    What they doThe technician checks that the electrode is correctly placed and free of scale, and cleans it only with a non-metallic bristle brush, as Cointra requires.

    They must show youthe electrode and its position.

    In writingwhether it was cleaned or replaced and why.

  3. Combustion check and calibration

    What they doWith an analyser, the technician measures CO2 in the flue gases at maximum and minimum output against the Cointra table and, after replacing the electrode, burner, gas valve or board, runs the 100 % calibration.

    They must show youthe analyser printout.

    In writingthe measured values against the manufacturer's specification and whether calibration was done.

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.

  1. Gas or flue gas smell before anything else

    No special tools

    Who:
    you.
    How:
    without touching switches, notice whether there is a smell of gas or flue gases near the boiler.
    Result that matters:
    whether there is a smell.
    If you smell gas or flue gases:
    do not reset; follow the warnings on this page.
    If there is no smell:
    check the flue terminal.
    Evidence to keep:
    a note of the time and what you noticed.

    Evidence: Cointra SUPERLATIVE PLUS 24 C, instrucciones de uso, instalación y mantenimiento

  2. Flue terminal and condensate drain, from outside

    No special tools

    Who:
    you.
    How:
    from the ground or a window, look at the air and flue terminal and, if visible, the condensate pipe, without touching anything or climbing.
    Result that matters:
    whether they are blocked, frozen or damaged.
    If you see a blockage:
    tell the technician; Cointra lists blocked ducts and siphon.
    If they are clear:
    it points to the electrode or the burner.
    Evidence to keep:
    photos of the terminal and the pipe.

    Evidence: Cointra SUPERLATIVE PLUS 24 C, instrucciones de uso, instalación y mantenimiento

  3. One reset with the reset key

    No special tools

    Who:
    you.
    How:
    press the reset key for one second, as Cointra describes for A letter faults. Do it once.
    Result that matters:
    whether the boiler restarts and holds the flame.
    If it restarts and A06 does not return:
    note the date; if it repeats, call the technician.
    If it does not restart:
    Cointra says the fault must be fixed; call an authorised technician.
    Evidence to keep:
    a photo of the display with A06 and the time.

    Evidence: Cointra SUPERLATIVE PLUS 24 C, instrucciones de uso, instalación y mantenimiento

  4. Electrode, burner, siphon and duct check by the technician

    Tools required

    Who:
    authorised gas technician.
    How:
    checks the position and condition of the ionisation electrode, the burner, the siphon and the air and flue ducts.
    Result that matters:
    which of the Cointra causes is present.
    If the electrode is out of position or scaled:
    that cause is confirmed.
    If the electrode and ducts are fine:
    it points to an unstable flame or the siphon.
    Evidence to keep:
    a report of what was checked, any part replaced and the analyser printout.

    Cointra reserves repairs and part replacement for authorised technicians: electrode, burner, internal siphon and ducts are not the user's job.

    Evidence: Cointra SUPERLATIVE PLUS 24 C, instrucciones de uso, instalación y mantenimiento

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
Cointra
Product type
Gas boiler

Known code variants

  • A-06
  • A6
  • Anomalía A06 Ferroli
  • Beretta A 06
  • Ciao Green A06
  • Cointra A 06
  • Error A06 Beretta
  • Error A06 Cointra
  • Error A06 Ferroli
  • Ferroli A06 caldera
  • Superlative A06

What it means

In the Superlative Plus fault table, A06 means no flame after the ignition phase. Cointra lists as possible causes an ionisation electrode fault, an unstable flame, blocked air or flue ducts and a blocked condensate siphon. The ionisation electrode is what tells the board a flame is present. The letter A means a permanent lockout that is cleared with the reset key. The code does not say which of those causes is at work.

Warnings and stop conditions

  • Criticaleditorial warning

    If you smell gas, do not reset: do not touch switches or light flames, open windows, close the gas tap if it is within reach, leave and call your gas distributor's emergency number from outside. Cointra says to switch the boiler off when it fails and to have it repaired only by an authorised technician.

    Evidence: Cointra SUPERLATIVE PLUS 24 C, instrucciones de uso, instalación y mantenimiento

  • Criticaleditorial warning

    Cointra warns of a risk of asphyxia from escaping flue gases if the boiler runs with the siphon empty. If you get a headache, dizziness or nausea, switch the boiler off, ventilate, leave the home and get help. A CO alarm near the boiler warns earlier.

    Evidence: Cointra SUPERLATIVE PLUS 24 C, instrucciones de uso, instalación y mantenimiento

  • Highsource verified

    Do not chain resets with A06: if the boiler does not restart, Cointra says the fault must be fixed. Do not open the boiler or touch the electrode, burner, siphon or ducts.

    Evidence: Cointra SUPERLATIVE PLUS 24 C, instrucciones de uso, instalación y mantenimiento

Symptoms and causes

Probable causes · in order

  • Ionisation electrodePossible

    Cointra says to check the position of the ionisation electrode and replace it if needed. It fits if the boiler lights and the flame is lost straight away.

    Evidence: Cointra SUPERLATIVE PLUS 24 C, instrucciones de uso, instalación y mantenimiento

  • Unstable flamePossible

    Cointra says to check the burner. It stands apart because a flame exists but does not hold; only the technician sees it with the boiler open.

    Evidence: Cointra SUPERLATIVE PLUS 24 C, instrucciones de uso, instalación y mantenimiento

  • Blocked air or flue ductsPossible

    Cointra says to clear the chimney, the ducts and the terminals. It fits with ice, nests or objects in the outside terminal.

    Evidence: Cointra SUPERLATIVE PLUS 24 C, instrucciones de uso, instalación y mantenimiento

  • Blocked condensate siphonPossible

    Cointra lists a blocked siphon and says to clean it. It fits if the condensate pipe does not drain or there is water where there should not be.

    Evidence: Cointra SUPERLATIVE PLUS 24 C, instrucciones de uso, instalación y mantenimiento

Virtual technician

Does A06 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.

Start diagnosis

Sources and technical references

  1. 1

    Cointra SUPERLATIVE PLUS 24 C, instrucciones de uso, instalación y mantenimiento

    Cointra · 2017 · manual

Sources: Cointra SUPERLATIVE PLUS 24 C, instrucciones de uso, instalación y mantenimientoreviewed 2026-10-04 · verified

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