Error code
Vaillant Boiler Fault Code F28
Quick answer
F28
The boiler has failed to ignite properly
First safe action
Check whether other gas appliances appear to have lost supply, without dismantling the boiler.
Meaning
Vaillant boiler fault code F28 usually means the boiler could not ignite or complete its startup sequence correctly.
Likely causes
- Temporary gas supply interruption
- Ignition or electrode fault
- Control problem affecting startup
Safe first checks
- Check whether other gas appliances appear to have lost supply, without dismantling the boiler.
- If the manufacturer permits a user reset, try the standard reset process once.
- Stop further reset attempts if the fault returns.
How to reset
- Follow the reset instructions shown on the boiler control panel or in the manual.
- If the code reappears after one reset, book a qualified engineer.
When to call an engineer
If the fault returns after one reset, stop there and arrange a Gas Safe registered engineer.
Safety warning
Do not remove the boiler casing or try to work on gas, ignition, or combustion components yourself.
Useful hub links
Related fault codes
F24 for Vaillant Boiler
Water circulation or pump performance issue
F27 for Vaillant Boiler
Flame detection has been lost during operation
F29 for Vaillant Boiler
Flame detection has been lost during operation
F32 for Vaillant Boiler
Fan, flue, or air pressure sensing problem
F23 for Vaillant Boiler
System water pressure is too low
F54 for Vaillant Boiler
Gas supply control or gas valve issue
Relevant guides
Frequently asked questions
Can I keep resetting a Vaillant boiler with F28?+
No. If F28 returns after one standard user reset, stop there and arrange a qualified engineer if the manual gives no safe next step.
Is F28 something I can repair myself?+
Boiler faults should be treated cautiously. Stay within the user checks in the manual, and leave gas, combustion, and internal boiler repairs to a qualified professional.