Baxi 2 Green Flashes Fault Code: Causes, Fixes & Repair Costs
What does the Baxi 2 Green Flashes fault code mean?
Two green flashes is not listed as a defined fault code in Baxi's standard LED flash-sequence documentation. The officially documented green flash codes are: 1 flash (target temperature reached — normal operation), 3 flashes (temporary flame loss — usually self-correcting), 4 flashes (communication error between PCB and controls — usually self-correcting), 5 flashes (parameter error on the PSU or PCB — usually self-correcting), and 6 flashes (miscellaneous error). If your boiler appears to be flashing green twice and behaving abnormally, the most likely explanations are: you are watching a combined red-and-green flash pattern (common on models such as the Baxi 35/80), your specific model variant uses a slightly different sequence not covered in the standard table, or the light is cycling in a non-fault rhythm rather than counting discrete flashes. In every case, cross-reference your boiler's own installation manual for the definitive flash-code list. Where the boiler is genuinely misbehaving, the underlying problems are most often low system pressure, poor water circulation, an ignition or gas supply issue, a frozen condensate pipe, or a PCB fault causing misleading flash behaviour.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Low system pressure Common
When boiler pressure drops below around 1 bar, the boiler struggles to circulate water properly and will often display a flash or warning indication. This is one of the most frequent triggers for unexpected green flash behaviour on Baxi boilers. Check the pressure gauge on the front panel — it should sit between 1 and 1.5 bar during normal operation.
- Frozen condensate pipe Common
During cold spells, the plastic condensate pipe that runs outside the property can freeze solid, preventing the boiler from draining waste gases and causing it to lock out or flash. This is extremely common in winter and is one of the few faults a homeowner can safely resolve themselves.
- Airlock or poor circulation Sometimes
Air trapped in the heating circuit can prevent water from flowing freely around the system. The pump may be running but moving little or no water, which can confuse the boiler's sensors and trigger abnormal flash patterns. Bleeding radiators is a straightforward first step.
- Ignition or gas supply problem Sometimes
If the boiler is attempting to fire but failing to establish a flame — due to a weak gas supply, a faulty ignition electrode, or a gas valve issue — it may flash and shut down. Check that other gas appliances in the home are working before assuming the boiler is at fault.
- PCB fault causing incorrect flash display Rare
A failing printed circuit board can produce erratic LED behaviour that does not correspond to any documented code. If the board itself is malfunctioning, the flash count you observe may not accurately represent the underlying fault — making diagnosis harder without specialist test equipment.
How to fix it
- Count the flashes carefully and consult your boiler manual DIY safe
Before doing anything else, watch the LED closely and count the flashes in a single sequence, including any red flashes that may accompany the green ones. Then compare your findings against the fault-code table in your boiler's specific installation or user guide. Two green flashes does not appear in the standard Baxi table, so your manual may reveal a model-specific meaning or confirm you are seeing a different pattern.
- Check the system pressure gauge DIY safe
Look at the pressure gauge on the boiler's front panel. A healthy reading is between 1 and 1.5 bar. If it reads below 1 bar, the system needs repressurising. Locate the filling loop — usually a flexible braided hose with one or two lever valves beneath the boiler — turn off the boiler, slowly open the valves until the gauge reaches around 1.2 bar, then close the valves firmly and switch the boiler back on.
- Reset the boiler (up to 2–3 times only) DIY safe
Turn the control dial to the reset position and hold it for approximately six seconds until you hear the boiler attempt to restart, then return the dial to your preferred heating setting. Wait a few minutes to see whether normal operation resumes. Do not reset more than two or three times in quick succession — repeated lockouts without a successful restart suggest an underlying fault that needs engineer investigation.
- Bleed the radiators to release any trapped air DIY safe
Work through each radiator in the home, starting on the ground floor. Use a radiator key to open the bleed valve slightly until water (not air) runs out steadily, then close the valve. After bleeding all radiators, recheck and if necessary top up the system pressure to 1.2 bar via the filling loop, as bleeding often causes a small pressure drop.
- Check whether other gas appliances are working DIY safe
Turn on a gas hob ring or another gas appliance. If it also fails to light, the issue is likely with your gas supply rather than the boiler itself — contact your gas supplier or call the National Gas Emergency Service on 0800 111 999. If other appliances work fine, the fault is isolated to the boiler.
- Thaw a frozen condensate pipe (winter only) DIY safe
If it is freezing weather and the boiler has stopped working, locate the white plastic condensate pipe that exits the property — often through an outside wall or into a drain. Gently pour warm (not boiling) water along its length, or hold a hot water bottle against the frozen section. Once the ice has cleared, reset the boiler as described above. Consider lagging the pipe afterwards to prevent a repeat.
- Call a Gas Safe registered engineer if the fault persists Gas Safe engineer
If the boiler continues to flash, fails to fire, or loses pressure repeatedly after you have tried the steps above, stop resetting it and contact a Gas Safe registered engineer. Faults involving the gas valve, ignition components, the pump, sensors, or the PCB all require professional diagnosis and repair. You can verify any engineer's credentials at www.gassaferegister.co.uk before they arrive.
Parts you may need
- Baxi PCB (printed circuit board) · from £220
- Circulating pump · from £85
- Ignition electrode and lead assembly · from £35
- Condensate pipe lagging kit · from £12
- Filling loop assembly · from £25
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £90–£320, depending on the underlying cause.
Frequently asked questions
Is 2 green flashes actually a Baxi fault code?
Not according to the standard Baxi LED flash-sequence documentation used by Gas Safe engineers. The listed green flash codes are 1, 3, 4, 5, and 6 flashes. Two green flashes does not appear in the official table. If you are seeing two green flashes, it is worth checking whether your boiler is actually showing a combined red and green pattern (as some models such as the Baxi 35/80 do), or whether the light is cycling continuously rather than counting a specific fault number. Always refer to your individual boiler's manual, as older or less common model variants can differ.
My Baxi is flashing green and I have no heating or hot water — what should I do?
Start with the basics: check the system pressure gauge (it should read 1–1.5 bar), bleed the radiators if the pressure is fine, and perform a single reset. In winter, check whether the condensate pipe has frozen. If the boiler still does not fire after one or two reset attempts, call a Gas Safe registered engineer. Repeated lockouts without recovery usually point to a component fault — such as an ignition problem, a faulty sensor, or a gas valve issue — that a homeowner cannot safely diagnose or repair.
How much will it cost to fix a Baxi boiler flashing green?
Most repairs that cause unusual green flash behaviour — including repressurising, a pump replacement, or an ignition component — typically cost between £90 and £320 including labour and parts. Simple jobs such as repressurising the system can take just a few minutes and sit at the lower end of that range, while replacing a pump or ignition assembly will cost more. Note that engineer call-out fees alone are typically £60–£100 for an independent Gas Safe engineer, or £99 and above for larger firms. More significant components such as a PCB (around £220–£350 installed) or a heat exchanger can cost considerably more, but these are less common causes of green flashing.
Can I fix a Baxi green flash fault myself?
Some checks are safe for a homeowner: topping up system pressure via the filling loop, bleeding radiators, thawing a frozen condensate pipe, and performing a boiler reset. If any of these resolve the issue, no engineer visit is needed. However, anything involving the gas valve, ignition components, the PCB, the pump internals, or any gas pipework must be carried out by a Gas Safe registered engineer. Attempting gas-related repairs without the correct registration is illegal in the UK and will invalidate your boiler warranty.