BoilerFaultCodesDaikin 12 Fault Code
The Daikin 12 fault code means: your boiler has detected trapped air inside the pipes or a sensor issue, which is preventing it from heating your water correctly.. It appears on 3 Daikin models in our database.
Technical description: Sensor fault S1: Air in the installation. Purge the air from the boiler and CH installation. Check the connection of the ntc on the hot water tube. Check wiring for break. Replace S1.
DIY fix possible
Check the boiler pressure gauge and top up to 1.5 bar if it is lowBleed your radiators using a radiator key to remove trapped airRestart the boiler to see if the fault clears
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Daikin models that show the 12 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Daikin 12 fault code information on this page is sourced and cross-checked against the official Daikin service / installation manuals for each affected model.
- Daikin Altherma Hybrid EHYKOMB33 manual (PDF)
- Daikin EKOMB 22 Combi manual (PDF)
- Daikin EKOMBG 22 manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026