Verified boiler fault code
Vaillant F.28 Fault Code (ecoTEC plus/pro (manual models))
The appliance does not start: attempts to ignite during start failed.
Safety disclaimer
Fault code summary
- Manufacturer
- Vaillant
- Fault code
- F.28
- Fault type
- Ignition, Flame failure, Gas supply
- Severity
- high
- Reset
- The operating instructions say the user may press the fault-clearance key for one second for another ignition attempt; do not repeatedly reset an unresolved fault.
- Applicable models
- ecoTEC plus 612, ecoTEC plus 615, ecoTEC plus 618, ecoTEC plus 624, ecoTEC plus 630, ecoTEC plus 637, ecoTEC plus 824, ecoTEC plus 831, ecoTEC plus 837, ecoTEC pro 28
Quick answer
The appliance does not start: attempts to ignite during start failed.
What does this fault code mean?
The appliance does not start: attempts to ignite during start failed.
Common causes
- Gas meter or gas pressure detector defective.
- Air in gas.
- Gas flow pressure too low.
- Fire protection tap disengaged.
- Gas valve, igniter, ionisation, earthing or electronics fault.
Symptoms
- The appliance does not start.
What can the homeowner safely check?
- Check whether other gas appliances are working and whether the gas supply is on, without working on the boiler.
Boiler reset information
The operating instructions say the user may press the fault-clearance key for one second for another ignition attempt; do not repeatedly reset an unresolved fault.
When should I call an engineer?
Contact a suitably qualified heating engineer when the fault persists, the boiler locks out, or the manufacturer instructions do not resolve it. For gas appliance work in the UK, use a Gas Safe registered engineer.
Engineer diagnosis
- Investigate gas supply, ignition, ionisation, earthing, gas valve and electronics.
Applicable boiler models
Related fault codes
- F.22 — ecoTEC plus/pro (manual models)
Dry fire.
Read fault code - F.23 — ecoTEC plus/pro (manual models)
Water shortage; the temperature difference between flow and return NTC is too large.
Read fault code - F.24 — ecoTEC plus/pro (manual models)
Water shortage; temperature rise too quick.
Read fault code - F.25 — ecoTEC plus/pro (manual models)
Interruption in the compact thermal module cable harness.
Read fault code - F.29 — ecoTEC plus/pro (manual models)
The flame goes off during operation and subsequent ignition attempts fail.
Read fault code - F.32 — ecoTEC plus/pro (manual models)
Fan speed variation.
Read fault code - F.49 — ecoTEC plus/pro (manual models)
eBUS undervoltage.
Read fault code - F.61 — ecoTEC plus/pro (manual models)
Gas-valve control defective.
Read fault code
Manufacturer documentation
Instructions for installation and servicing ecoTECF.28 | Appliance does not start: Attempts to ignite during start failed | Faults in the gas supply ... gas valve ... igniter ... ionisation current ... faulty earthing ... electronics defective
Last verified
2026-09-12
Frequently asked questions
What does Vaillant F.28 mean?
The appliance does not start: attempts to ignite during start failed.
Can I reset a Vaillant F.28 fault?
The operating instructions say the user may press the fault-clearance key for one second for another ignition attempt; do not repeatedly reset an unresolved fault.