Do not keep resetting the boiler. This code points to a gas, flue or combustion fault. Switch the boiler off and call a Gas Safe engineer. If you smell gas, call 0800 111 999 first.
Likely causes
- Faulty gas valve stepper motor
- Wiring or plug fault to the gas valve
- PCB fault
What you can safely check
- Reset the boiler once; if F.26 returns, leave the boiler off and call us
What our engineer does
We test the gas valve, its wiring and the PCB and replace the failed part, then check the gas valve for tightness. Anything involving the gas supply, gas valve, combustion chamber, flue, fan, PCB or heat exchanger must be left to a Gas Safe registered engineer and must not be attempted by the householder.
Models this applies to: Vaillant ecoTEC plus, Vaillant ecoTEC pro, Vaillant ecoTEC exclusive, Vaillant ecoFIT pure.
Boiler repairs from £90
Diagnosis and a fixed price before the repair. Most faults fixed on the first visit. Gas Safe 925538.
Other Vaillant codes
Guidance only. Fault codes vary by model and firmware; anything involving gas, the flue, the fan, the gas valve, the PCB or the heat exchanger must be done by a Gas Safe registered engineer.
