Error 3 Red Flashes

Safety first

1) If you smell gas, do not touch the boiler or any electrical switches. Open windows, evacuate the property, and call your gas emergency number immediately. Do not attempt to relight the boiler.

2) If you see water leaking or damage, isolate water and electricity to the boiler and call an engineer. Do not open the boiler casing or attempt internal repairs.

Initial checks you can safely do

1) Check the gas supply: verify other gas appliances (hob) work and the gas meter or supply has not been turned off. If you use a prepayment meter, check credit.

2) Check the boiler pressure gauge. Aim for around 1.0–1.5 bar when cold. If pressure is below 1 bar, top up with the filling loop following the user manual and then reset the boiler. If pressure is low repeatedly, call an engineer.

3) Check external vents and the flue terminal for obvious blockages (birds’ nests, debris) and ensure air vents around the boiler are not blocked.

4) Note the exact fault indication and any other lights or codes. Try to remember whether the boiler attempts to fire (clicking) or is completely silent.

How to attempt a controlled reset (one time)

1) Locate the reset button or selector on your MainEco control panel. Hold the reset button for 5–10 seconds as described in the manual. Release and observe whether the boiler attempts to fire and whether the red flashes clear.

2) If the boiler restarts and operates normally, monitor for recurring faults. If the same lockout returns, stop resetting and call an engineer—repeating resets can worsen faults.

Further safe diagnostic checks (do not open the boiler)

1) With the power off and only if you are comfortable doing a visual check from outside the casing, look for obvious signs: soot around the flue, signs of water ingress, loose external wiring connectors, or burn marks. Do not touch internal components.

2) In cold weather check the condensate pipe (if visible outside) for freezing; a blocked condensate can cause ignition problems on some models. If frozen, thaw with warm water (not boiling) and try a reset.

What a Gas Safe engineer will check and likely do

1) Confirm gas supply pressure and meter/house supply. 2) Inspect and test ignition electrodes/ignition leads and replace if worn or damaged. 3) Test and clean or replace the flame sensor/ionisation probe. 4) Test the gas valve and combustion components and check burner condition and chamber seals. 5) Check the fan and flue pressure/sensor and the PCB/controls if required.

When to call a professional

1) If reset does not clear the lockout, if the fault returns after a reset, if you are not confident doing the basic checks, or if there is any sign of gas smell or water leak, call a Gas Safe registered engineer. 2) Tell the engineer the boiler model, the exact symptom (3 red flashes / ignition fault), what checks you have already done (gas supply, pressure, reset attempts) and any other codes or noises observed.

Final notes

1) Do not attempt internal repairs or replace ignition or gas components yourself. 2) Avoid repeated resets—one controlled reset to test is acceptable, but recurring lockouts need professional diagnosis. 3) Keep the boiler manual and the engineer’s contact to hand for any call-out.