Overview
The 6 red flashes on a Baxi MainEco indicate a 'miscellaneous' fault. This is a general, catch‑all lockout that the boiler uses when it detects a problem it cannot categorise under a specific fault code. The underlying cause can range from temporary sensor or communication glitches to more significant component faults (PCB/parameter errors, wiring, fan/gas valve issues, false flame signals or other internal faults). Because it’s a miscellaneous code, it does not point to a single defined component — further investigation is required. Severity can vary. Sometimes a 6 red flash is a temporary fault that clears after a reset (low pressure, transient sensor error, frozen condensate pipe or a brief communication glitch). Other times it indicates a persistent internal or safety fault that will lock the boiler out and needs a Gas Safe engineer. If the boiler is locked out you will usually have no heating or hot water until the underlying cause is fixed. If you smell gas or suspect a carbon monoxide issue, treat it as an emergency and follow the emergency procedures below. Homeowner action is limited. You can safely perform basic checks and a controlled reset to see if the fault clears. Do not open the boiler casing or attempt repairs to gas components, PCB, wiring, fan or gas valve unless you are a qualified engineer. For any persistent fault, repeated lockouts, or if you are unsure, you must call a Gas Safe registered engineer.
Possible Cause: Miscellaneous
Troubleshooting Steps
Safety precautions:
1. If you smell gas or suspect a gas leak: do not operate electrical switches, evacuate everyone from the property immediately and call the national gas emergency number. Get the property ventilated from a safe location.
2. If you or household members have symptoms of carbon monoxide exposure (headache, nausea, dizziness) or see soot or yellow flames, turn off the boiler at the isolator, open windows, leave the building and call emergency services and a Gas Safe engineer.
3. Only carry out non-invasive checks. Do not remove the boiler cover, do not tamper with gas connections, and do not attempt electronic repairs. If in doubt, call a qualified engineer.
Initial checks the homeowner can do:
1. Note exactly what the display shows (6 red flashes) and when it happened, and take a photo for the engineer.
2. Check the boiler display message or action log if your model shows more detail.
3. Check mains power to the boiler and reset any tripped RCD or fuse. Ensure the boiler is powered.
4. Confirm the gas supply is on at the meter or gas shut-off tap and that any prepayment meter has credit.
5. Check system water pressure on the boiler gauge—aim for around 1.0–1.5 bar cold. If pressure is low, follow the manufacturer’s instructions to top up via the filling loop. Only top up if you know how; do not over-pressurise.
6. Check outside of the house for blocked flue terminal, vents, or debris that could affect ventilation. Check if condensate pipe appears frozen in cold weather (frozen condensate is common in winter).
Reset procedure (try once):
1. Try a controlled reset first. Locate the reset button or selector on your MainEco boiler (reset button or 'R' on the selector). Press and hold the reset for about 5–10 seconds as described in the manual. Some models require turning a selector to R and holding for 5 seconds.
2. After reset, allow the boiler to complete its start sequence. Listen for the fan and ignition attempts. If the boiler restarts and runs normally, monitor it for a day to ensure the code does not reoccur.
3. Do not repeatedly reset the boiler more than 2–3 times. Repeated resets can hide a persistent fault and may make diagnosis harder for the engineer.
If reset does not clear the fault, step-by-step diagnostics you can check safely:
1. Pressure and circulation: Re-check system pressure. If low, top up and then try a reset. Bleed a radiator or two to remove trapped air if circulation seems poor. If pressure keeps dropping, this indicates a leak or fault and needs an engineer.
2. Condensate pipe: In freezing weather check for a frozen condensate pipe. Thaw it with warm (not boiling) water or a hot water bottle, then reset the boiler. Do not use open flames or excessive heat.
3. External flue/venting: Clear any visible blockages (leaves, bird nests) at the flue terminal. If the fan cannot vent, the boiler may lock out.
4. Observe start-up: When you call for heat/hot water, listen for the fan running and ignition attempts. No fan noise or repeated ignition attempts may indicate fan, gas valve, or ignition components are faulty — these are not homeowner repairs.
5. Visual checks: With power off only, check for any obvious wet areas, signs of leaks, or disconnected external pipework or cables. Do not open internal wiring or the boiler case.
When to call a professional (and what to tell them):
1. Call a Gas Safe registered engineer if the 6 red flashes persist after basic checks and a reset, or if the code returns frequently. Also call if you are not comfortable performing the checks above.
2. Tell the engineer the exact code (6 red flashes), any additional display messages, when it started, recent events (power cuts, freezing weather, servicing history), water pressure reading, and whether a reset was attempted.
3. The engineer will carry out safe internal diagnostics: check PCB logs and parameters, sensors (NTCs), fan, PSU, gas valve and ignition system, wiring and connectors, condensate arrangements, and replace faulty components or update parameters as required. These are specialist tasks and should only be done by a qualified engineer.
Final notes:
1. Do not attempt internal repairs, PCB replacement or gas component work yourself. These tasks require a Gas Safe engineer.
2. If the boiler is under warranty or on a service plan, inform the manufacturer/servicer and the engineer.
3. If the fault is intermittent, keep a simple log (date/time/what was happening) to help the engineer diagnose the pattern.
4. If at any stage you smell gas or suspect carbon monoxide, follow the safety steps at the start and contact emergency services and Gas Safe immediately.
Helpful Resources
Boiler Manual
Download the official PDF manual for the Baxi MainEco.