How much does it cost to fix Vaillant error code F.28?

Typical repair cost for the Vaillant F.28 fault is £100-350 including labour.

F.28 High

Vaillant F.28 Fault Code

Q: What does the Vaillant F.28 fault code mean?

Your boiler is failing to light because it isn't receiving gas or the ignition system isn't creating a spark.

Also written as F28 — same fault.

The Vaillant F.28 fault code means: your boiler is failing to light because it isn't receiving gas or the ignition system isn't creating a spark.. It appears on 68 Vaillant models in our database.

Technical description: Boiler goes to lock out | No gas, Insufficient gas, Incorrect gas valve adjustment, Electrode defective, Ignition lead defect, Electronic igniter defective

What causes the Vaillant F.28 fault?

This fault occurs when the boiler attempts to ignite several times but fails to establish a flame, leading the system to shut down for safety. The most common reasons are a lack of gas reaching the unit, a worn-out spark electrode that can no longer light the burner, or a faulty gas valve failing to open. In some cases, it can be caused by something as simple as a recent gas meter exchange or the gas supply being temporarily turned off.

This fault often appears during the first cold snap of winter when components like the gas valve or ignition leads are put under sudden strain after being idle over summer.

Typical repair cost £100-350 (including labour)

DIY fix possible

Check that your gas meter has credit and the isolation valve is openCheck if other gas appliances, like a cooker, are workingPress the reset button (flame symbol with a cross) for one second

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Vaillant models that show the F.28 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Vaillant F.28 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026