The Vaillant ecoTEC Pro and Plus display fault codes prefixed with "F" when they detect an issue. Here's how to handle the most common ones.
How to reset a Vaillant ecoTEC
- Note the fault code displayed
- Press the reset button — marked with a flame and arrow symbol, or on the ecoTEC Pro/Plus, hold the "i" button for 3 seconds
- The boiler will attempt an ignition cycle
- Allow 2–3 minutes for the restart sequence
Common Vaillant fault codes
- F.22: Low water pressure — re-pressurise to 1–1.5 bar, then reset. Most common fault after summer when heating hasn't been run.
- F.28: Ignition failure — gas supply issue or igniter fault. Check other gas appliances work. If yes, call an engineer.
- F.29: Flame loss — similar to F.28. Engineer required if persists.
- F.75: Pressure sensor or pump fault — engineer required
- F.83: Flow or return temperature sensor fault — engineer required
The Vaillant pressure check
F.22 (low pressure) is by far the most common Vaillant lockout. Always check the pressure gauge first — it's the small circular gauge on the front of the boiler, usually behind a flap. If it reads below 1 bar, re-pressurise before calling anyone.
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