BoilerFaultCodesBaxi 1 flash red Fault Code
Also written as 1FLASHRED — same fault.
The Baxi 1 flash red fault code means: your boiler has detected that water is either not moving through the system correctly or a temperature sensor has failed, preventing it from heating up safely.. It appears on 4 Baxi models in our database.
Technical description: Sensor error: Bad connection to flow or return temperature sensor, Fault with flow or return temperature sensor(s), Low or no flow through boiler, Reverse flow through boiler
DIY fix possible
Check that your central heating valves (under the boiler) are fully openEnsure all radiator valves are turned on to allow water to flowReset the boiler by turning the selector switch to the 'R' position for five seconds
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Baxi models that show the 1 flash red fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Baxi 1 flash red fault code information on this page is sourced and cross-checked against the official Baxi service / installation manuals for each affected model.
- Baxi 613 Heat manual (PDF)
- Baxi 800 Heat (range) manual (PDF)
- Baxi EcoBlue Advance Heat manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026