Vaillant Boiler Fault Code F28: Failure During Ignition / No Gas Supply
The boiler made 3 ignition attempts but failed to detect a flame, locking out for safety.
Equipment TypeGas Combi & System BoilerBrand: Vaillant
Fault SeverityCriticalSystem Lockout Active
Estimated Repair Cost£95 – £320Parts & Certified Labor
🚨 Symptoms of Vaillant Error F28
- Boiler displays F28 and locks out
- No central heating or hot water
- Boiler resets but fails again with clicking sounds
🔍 Root Causes for Vaillant Code F28
- Gas supply valve closed or frozen external gas regulator/pipe
- Defective spark electrode or ignition lead
- Faulty gas valve stepper motor not opening
- Dirty or defective flame rectification sensor (ionization electrode)
- Air in the gas supply line after maintenance
🛠️ How to Reset & Troubleshoot Vaillant Error F28
- Verify gas supply is turned on and other gas appliances (cooktop) work
- Check if condensate pipe is frozen outside in freezing weather
- Press the flame symbol reset button on the boiler fascia once
- Contact a Gas Safe / certified heating engineer to test gas valve pressure and replace ignition electrodes
Frequently Asked Questions — Vaillant Code F28
What does Vaillant error code F28 mean?
Vaillant code F28 indicates: The boiler made 3 ignition attempts but failed to detect a flame, locking out for safety.
How do I reset error code F28 on Vaillant?
Turn off the electrical circuit breaker or isolator to the unit for at least 5 minutes to discharge the capacitors and reset the microprocessor. If the code reappears immediately upon restarting, professional inspection is required.
What causes error code F28 on Vaillant systems?
Common triggers include: Gas supply valve closed or frozen external gas regulator/pipe, Defective spark electrode or ignition lead, Faulty gas valve stepper motor not opening.