BoilerFaultCodesMain 3 Red Flashes Fault Code
Also written as 3REDFLASHES — same fault.
The Main 3 Red Flashes fault code means: your boiler has tried to light itself several times but cannot create a flame, meaning you will not have any heating or hot water until it is reset or repaired.. It appears on 2 Main models in our database.
Technical description: Ignition fault. Boiler has attempted to light 5 times and failed
What causes the Main 3 Red Flashes fault?
This fault occurs when the boiler is unable to detect a steady flame after several attempts to ignite the gas. The most common reasons are a lack of gas supply reaching the unit, worn-out ignition components that can't create a spark, or a dirty internal sensor that cannot tell the boiler the flame is lit.
This fault is frequently seen during extreme cold snaps, as the external condensate pipe can freeze and back up into the boiler, preventing the ignition process.
DIY fix possible
Check that your gas emergency control valve is open and you have credit on your gas meterTurn the selector switch to the 'R' (Reset) position for at least five secondsRelease the switch and see if the boiler initiates a successful ignition sequence
Find a Gas Safe engineer
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Gas Safe Register →Avoid the next call-out bill
A cover plan would handle faults like 3 Red Flashes: no call-out fees, no surprise bills.
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Main models that show the 3 Red Flashes fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Main 3 Red Flashes fault code information on this page is sourced and cross-checked against the official Main service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026