Overview
On a Baxi EcoBlue Advance / Ecoblue Regular gas boiler, a single green flash normally indicates that the boiler has reached the temperature you requested and is operating as intended. It is not a fault code but a status indicator showing that the boiler has cycled off because the set temperature has been met or the hot water/central heating demand has been satisfied. This condition is low severity and usually needs no action. If the boiler and heating/hot water are working normally, you can ignore a single green flash. Contact a qualified Gas Safe registered engineer only if the single green flash is accompanied by loss of heating or hot water, other warning lights or fault codes (especially red flashes), persistent abnormal behaviour, or if you smell gas or suspect carbon monoxide exposure.
Possible Cause: Boiler temperature reached. No action required.
Troubleshooting Steps
Safety first: If you smell gas, leave the property immediately and call the gas emergency number. If you or anyone in the property has symptoms of carbon monoxide poisoning (headache, dizziness, nausea), get fresh air and seek medical help, and do not use the boiler. Do not open or dismantle the boiler or its sealed components. Turn off electrical supply at the isolator if you must work near the unit, but do not attempt internal repairs; only a Gas Safe registered engineer should work on gas or combustion components.
Initial homeowner checks you can do:
- Confirm the heating and/or hot water are behaving as expected (radiators and taps get hot to the expected level). A single green flash is normally just confirmation that the demand has been met.
- Check the room thermostat and programmer settings to ensure the set temperature and schedules are correct.
- Look at the boiler pressure gauge: it should normally read around 1.0–1.5 bar when cold. If pressure is very low or very high, that can cause other issues.
- Scan the boiler control panel for any other lights or fault codes (especially red flashes or E-codes). Make a note of them if present.
- Check external flue and air intake for obvious blockages and the condensate pipe in cold weather for freezing.
Specific diagnostic and simple fix steps you can try:
1) If the system is working normally: do nothing. A single green flash simply means temperature achieved and the boiler is in normal standby mode.
2) If radiators or hot water are not reaching expected temperature even though the boiler shows 1 green flash, confirm thermostat setpoint and all radiator TRVs/valves are open. Bleed radiators to remove trapped air that can reduce flow.
3) If system pressure is below about 1.0 bar, top up using the filling loop: locate the flexible filling loop or integrated valve under the boiler, open the two filling valves slowly while watching the gauge until pressure is about 1.0–1.5 bar, then close both valves and secure the loop. Only do this if you are confident; if unsure, call a professional.
4) If you have recently reset the boiler or it has cycled frequently, try a single reset: press and hold the boiler reset button or set the selector to R and hold for around 5 seconds. Do not repeatedly reset if the boiler locks out again.
5) If the condensate pipe is frozen in cold weather, thaw it with warm (not boiling) water or a warm cloth and then restart the boiler.
When to call a professional:
- If other fault indicators or error codes appear, especially red flashes or E-codes.
- If the boiler locks out repeatedly or will not fire when called for heat or hot water.
- If system pressure repeatedly drops or there are signs of a leak, unusual noises, smells, or suspected carbon monoxide.
- For any internal component issues, gas valve, ignition, PCB, fan or sensor faults.
A Gas Safe registered heating engineer should diagnose and repair these faults. If in doubt at any stage, stop and contact a qualified engineer to avoid safety risks.
Helpful Resources
Boiler Manual
Download the official PDF manual for the Baxi EcoBlue Advance / Ecoblue Regular Gas Boiler.