Likely causes
- Pump blocked or running at low output
- Air in the system
- Closed valves or a blockage
- Flow or return sensor fault
What you can safely check
- Check the pressure gauge or display and top up to between 1 and 1.5 bar if it is low, then close the filling loop fully
- Bleed any radiators that are cold at the top, then check the pressure again
- Reset the boiler once
What our engineer does
We check the pump, vent the system, clear any blockage and test both temperature sensors. 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.
