BoilerFaultCodesBaxi FLASH OFF ON Fault Code
Also written as FLASHOFFON — same fault.
The Baxi FLASH OFF ON fault code means: your boiler has shut down because it has become too hot and needs to be safely reset after cooling down.. It appears on 3 Baxi models in our database.
Technical description: Overheat lockout
What causes the Baxi FLASH OFF ON fault?
This fault occurs when the water inside the heat exchanger exceeds a safe temperature limit, triggering a safety cutout to prevent damage. The most common reasons include a failing circulation pump that isn't moving heat away quickly enough or a blockage in the system pipework. It can also be caused by a faulty internal sensor incorrectly reading the temperature.
This issue often surfaces during the first cold spell of autumn when the heating is turned on after being dormant all summer, which can cause internal pump components to seize.
DIY fix possible
Turn the boiler thermostat knob to the 'OFF' position.Wait at least 10 seconds for the system to acknowledge the reset.Turn the thermostat knob back to your desired temperature setting.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Avoid the next call-out bill
A cover plan would handle faults like FLASH OFF ON: no call-out fees, no surprise bills.
Affiliate links. We may earn a commission at no extra cost to you.
Baxi models that show the FLASH OFF ON fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Baxi FLASH OFF ON fault code information on this page is sourced and cross-checked against the official Baxi service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026