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CP-017AppliancesMittel

Vaillant F28 Error: Ignition Failure and How to Fix It

Geschätzte Zeit: ~10 Min.5 SchritteZuletzt geprüft:

Independent guide — no official affiliation with the platforms mentioned.

Kurze Antwort

Vaillant F28 means 'ignition failure' — the boiler can't light the gas. Usually the gas valve is closed or there's a gas outage. Check the valve, reset the boiler; if it persists, the ignition electrode needs service.

01 — Schritt-für-Schritt-Lösung

Schritt-für-Schritt-Lösung

  1. STEP 01

    Check that the gas valve is open

    The valve handle under the boiler should be parallel to the pipe. If it's perpendicular, open it.

    If you smell gas: close the valve, don't touch electrical switches, leave the building and call the gas utility. Skip the steps below.

  2. STEP 02

    Check for a gas outage

    Try another gas appliance, like the stove. If nothing lights, there may be an outage — wait a few minutes and retry.

  3. STEP 03

    Reset the boiler

    Hold the reset button on the front panel for 2–3 seconds. The boiler retries ignition.

  4. STEP 04

    Check the water pressure

    System pressure should read 1.0–1.5 bar. Refill via the filling loop if it's low.

  5. STEP 05

    Call service if it fails 3 times

    If F28 returns after reset, the ignition electrode, gas valve or ionization measurement needs professional inspection.

Tipps

  • After long disuse, 2–3 resets may be needed to purge air from the gas line.
  • Skipping annual service accelerates electrode fouling — the second most common F28 cause.

02 — Häufig gestellte Fragen

Häufig gestellte Fragen

Does F28 go away by itself?

If it was caused by a gas outage, yes — reset after supply returns. Dirty electrodes cause recurring F28s that need service.

F28 vs F75 — what's the difference?

F28 is ignition (gas); F75 is a pressure sensor/pump fault. In F28 the boiler can't light; in F75 it lights but pressure readings are inconsistent.

Why does F28 appear in freezing weather?

In condensing models the condensate drain can freeze and lock the gas valve. Check that the drain's heating cable works.

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