BoilerFaultCodesVaillant F.28 Fault Code
Also written as F28 — same fault.
The Vaillant F.28 fault code means: your boiler is failing to light the flame after three attempts, which is usually caused by a gas supply issue or a component failure in the ignition system.. It appears on 45 Vaillant models in our database.
Technical description: Boiler goes to lock out | No gas; Isufficient 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 consistent flame. The most common reasons include a lack of gas reaching the burner, worn-out spark electrodes that can no longer create a flame, or a faulty gas valve that isn't opening correctly. This effectively acts as a safety shutdown to prevent the boiler from trying to operate without a fire.
This fault is more frequent during the first cold snap of winter, as gas valves and internal components can seize up after sitting idle during the summer months.
DIY fix possible
Check if other gas appliances, like a cooker, are working to ensure gas is reaching your home.Check if your prepaid gas meter (if applicable) has credit.Try resetting the boiler by pressing the flame symbol button or the reset button on the front panel.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Avoid the next call-out bill
A cover plan would handle faults like F.28: no call-out fees, no surprise bills.
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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.
- ecoFIT Pure 412 Repair: £150-350
- ecoFIT Pure 418 Repair: £150-350
- ecoFIT Pure 425 Repair: £150-350
- ecoFIT Pure 435 Repair: £150-300
- ecoFIT pure 612 Repair: £150-350
- ecoFIT pure 615 Repair: £150-350
- ecoFIT pure 618 Repair: £150-350
- ecoFIT pure 630 Repair: £150-350
- ecoFIT Pure 825 Repair: £150-350
- ecoFIT Pure 830 Repair: £150-350
- ecoFIT Pure 835 Repair: £150-350
- ecoFIT sustain 415 Repair: £150-350
- ecoFIT sustain 418 Repair: £150-350
- ecoFIT sustain 430 Repair: £150-350
- ecoFIT sustain 615 Repair: £150-350
- ecoFIT sustain 618 Repair: £150-350
- ecoFIT sustain 630 Repair: £150-350
- ecoFIT sustain 825 Repair: £150-350
- ecoFIT sustain 830 Repair: £150-350
- ecoFIT sustain 835 Repair: £150-350
- ecoMAX Repair: £100-£350
- ecoMAX 613 Repair: £120-280
- ecoMAX 618 Repair: £120-280
- ecoMAX 622 Repair: £120-280
- ecoMAX 635 Repair: £120-280
- ecoMAX 824/2 E Repair: £120-280
- ecoMAX 828/2 E Repair: £120-280
- ecoMAX 835 E Repair: £120-280
- Ecomax Condensing 600/800 series Repair: £150-350
- ecoTEC exclusive Repair: £90-350
- ecoTEC plus Repair: £100-£350
- ecoTEC plus VU GB 656/4-5 A Repair: £150-350
- ecoTEC pro Repair: £100-350
- ecoTEC sustain Repair: £100-350
- Home Combi 25 Repair: £150-350
- Home Combi 30 Repair: £150-350
- Home Combi 35 Repair: £150-350
- Home Regular 12
- Turbomax 824/828 Repair: £150-350
- Turbomax Plus Repair: £150-350
- Turbomax Plus 824/828E Repair: £100-280
- Turbomax Plus 828 Repair: £120-350
- Turbomax Plus 828 E Repair: £100-280
- Turbomax Plus VUW 242E Repair: £100-280
- Turbomax Plus VUW 242EH Repair: £100-280
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.
- Vaillant ecoFIT Pure 425 manual (PDF)
- Vaillant ecoFIT Pure 435 manual (PDF)
- Vaillant ecoFIT pure 630 manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026