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Buderus Fault Codes

Select a fault code to see its meaning, common causes and how to fix it.

• 4C Fault code 4C on a Buderus boiler signals that one or both of the built-in safety temperature limiters (STBs) —… Read more →
• 4U The Buderus 4U fault code indicates that the boiler's flow temperature sensor (NTC thermistor) has developed a short… Read more →
• 6A Fault code 6A on a Buderus boiler means the boiler attempted to light the burner but failed to detect a flame. After… Read more →
• 6L Fault code 6L on a Buderus boiler indicates that the flame-sensing (ionisation) electrode has failed to detect a stable… Read more →