What does the code indicate?
On a Vaillant boiler, code F.23 is associated by the manufacturer source with “Protection fault associated with insufficient water”. The code is a diagnostic clue, not proof that one specific part has failed; verify the exact model/series and when the code appears.
Safe check order
- Confirm the exact model/product code from the rating label.
- Photograph the code and any adjacent symbols.
- Do not dismantle the appliance beyond user procedures in the manufacturer manual.
When should use stop?
If gas is smelled, do not use the boiler. Close the gas valve if safe, ventilate, avoid electrical switches or open flames and contact the relevant gas emergency service. Also stop use for major water leakage, smoke or repeated electrical faults.
Model note
Model and series differences can change the meaning of an error code. Verify the product label and manufacturer documentation.
Manufacturer source: Vaillant Türkiye
Vaillant Boiler F.23Vaillant F.23 error code