BoilerFaultCodesChaffoteaux 12 Fault Code
The Chaffoteaux 12 fault code means: your boiler's internal thermometer for the heating system has stopped working, meaning the unit cannot safely tell how hot the water is and has shut down as a precaution.. It appears on 12 Chaffoteaux models in our database.
Technical description: Central Heating thermistor faulty (open circuit)
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Chaffoteaux models that show the 12 fault code
Click a model for the full fault code list and model-specific repair notes.
- Calydra 23 Green Repair: £90-160
- Calydra 24 Green Repair: £90-160
- Calydra Comfort 100 Repair: £120-220
- Celtic 2 24 Rsc Repair: £80-150
- Celtic 24 HE Repair: £80-250
- Centora Green 24 Repair: £120-200
- Centora Green 30 Repair: £120-200
- Centora Green System 24 Repair: £120-220
- Centora Green System 30 Repair: £120-200
- Sterling FF Repair: £80-150
- Talia Green 25 Repair: £120-220
- Talia Green System Repair: £120-220
Source
Chaffoteaux 12 fault code information on this page is sourced and cross-checked against the official Chaffoteaux service / installation manuals for each affected model.
- Chaffoteaux Calydra 24 Green manual (PDF)
- Chaffoteaux Calydra Comfort 100 manual (PDF)
- Chaffoteaux Celtic 2 24 Rsc manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026