Error 2 long flashes, 4 quick flashes, 5 second gap, 2 long flashes, 4 quick flashes

Safety precautions:

1) If you smell gas: do not operate electrical switches; turn off gas at the mains tap if safe to do so, leave the building, and call the national gas emergency number.

2) Before doing any work on or inside the boiler, turn off the boiler at the programmer and at the electrical isolator/mains and make sure the power is isolated. Internal inspections and electrical tests should only be carried out by a Gas Safe registered engineer.

3) Do not repeatedly reset the boiler; repeated resets can mask a persistent safety problem.

Initial checks a homeowner can do (non-invasive):

1) Note the exact error sequence and any other display/behaviour. Photograph the fault lights and the boiler data plate (model and serial) for the engineer.

2) Try a single basic reset: switch the boiler off at the programmer, switch off at the mains isolator for 30 seconds, then switch back on and attempt a single reset via the control knob or reset button. If the fault returns immediately or within a short time, stop and proceed to the next checks.

3) Check the flue terminal outside for obvious blockages (bird nest, debris, snow, leaves) and make sure the air intake/room ventilation louvres (if applicable) are open and not blocked. Clear any obvious external obstruction safely.

4) Check external condensate pipework for freezing or blockage (usually in cold weather a frozen condensate can cause fault sequences). Thawing frozen condensate should be done carefully with warm (not boiling) water. If the condensate pipe is blocked at ground level, clear it where safe to do so.

5) Look inside the boiler only for obvious loose plug connections (no tools, no power): with the boiler isolated and cover removed, check that the fan connector is seated and wires are intact. Do not touch live terminals and do not re-seat connectors while powered.

Specific diagnostic and fix steps (for a competent person / engineer):

1) Record fault history and any preceding events (power cuts, storms, recent maintenance). If a short power interruption preceded the fault, it can affect control electronics.

2) With appropriate isolation and safety, a Gas Safe engineer will check that the control board is commanding the fan and that correct mains supply is reaching the fan. They may measure voltage between the fan supply wires (typically the live/pulse wires as per manufacturer wiring) during start-up to confirm the board is driving the fan.

3) The engineer will inspect the fan motor, bearings and impeller for seizure, wear or obstruction and will check the fan tachometer/sensor feedback (used to monitor speed). Faulty bearings or seized motors normally require fan replacement.

4) The wiring harness and connector between the fan and the main PCB will be checked for corrosion, loose pins or damage; any damaged wiring or connectors should be repaired or replaced.

5) If the control board is not driving the fan correctly or the fan control electronics (inside the fan assembly) are faulty, the engineer may replace the fan assembly (often the simplest and most reliable repair) or replace control components as required.

6) If airflow is present but the boiler still detects incorrect flow (airflow sensor or pressure switches if fitted), the engineer will test those sensors and the related tubing/pressure switch for leaks or blockages and replace if needed.

When to call a professional and what to tell them:

1) Call a Gas Safe registered engineer if the fault does not clear after the simple checks, if you are not competent to work on gas/electrical appliances, or if the engineer’s diagnostics are required (measurements, fan replacement, PCB replacement).

2) When arranging the visit tell them: boiler model and serial, the exact flash sequence you recorded, when it started, whether a reset was attempted and what external checks you performed (flue clear, condensate thawed), and any smell of gas or recent power issues.

Final notes:

1) This is a safety-related fault and while some initial checks are suitable for homeowners, internal electrical testing and component replacement must be carried out by a Gas Safe engineer.

2) Repeated resets are not a permanent solution; persistent faults require professional diagnosis and repair.

3) If you are without heating or hot water and the boiler is locked out, use safe alternative heating and water sources until a qualified engineer can attend.