BoilerFaultCodesBaxi ON ON FLASH Fault Code
Also written as ONONFLASH — same fault.
The Baxi ON ON FLASH fault code means: your boiler's internal computer has developed a fault and can no longer control the heating process safely.. It appears on 24 Baxi models in our database.
Technical description: Printed circuit board (PCB) error
What causes the Baxi ON ON FLASH fault?
This fault occurs when the electrical components on the main control board suffer a critical failure, preventing the system from processing instructions correctly. The most common reason is general wear and tear over many years of use, though it can also be triggered by a sudden power surge or moisture getting into the casing.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Baxi models that show the ON ON FLASH fault code
Click a model for the full fault code list and model-specific repair notes.
- 130 HE (range) Repair: £250-450
- 400 Combi (range) Repair: £250-£450
- 800 Repair: £250-£450
- 80e Repair: £250-£450
- Assure Repair: £280-450
- Bermuda Repair: £280-450
- Eco Compact Repair: £250-450
- Eco Elite Repair: £280-450
- EP Repair: £280-450
- Netaheat Repair: £280-450
- Performa Repair: £250-450
- Profile Repair: £280-450
- Profile Prima Repair: £220-380
- Solo Repair: £280-450
- Statesman Repair: £280-450
- Suprima 100 Repair: £280-450
- Suprima 115 Repair: £240-£380
- Suprima 30 Repair: £240-380
- Suprima 40 Repair: £280-450
- Suprima 50 Repair: £280-450
- Suprima 60 Repair: £280-450
- Suprima 70 Repair: £240-380
- Suprima 80 Repair: £280-450
- Titanium Repair: £250-£450
Source
Baxi ON ON FLASH 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 27 April 2026