Error 1 Red Flash

Safety precautions:

1) If you smell gas or suspect a gas leak, get everyone out, do not operate electrical switches, and call the gas emergency service immediately. Do not attempt repairs. 2) If you are unsure, uncomfortable or the boiler shows signs of overheating, smoke, flames or leaks, shut the appliance down and call a Gas Safe engineer. 3) Always isolate electrical supply before opening covers or touching internal components; do not attempt internal electrical or gas work yourself.

Initial quick checks a homeowner can do:

1) Check the pressure gauge on the boiler when cold — the target is normally around 1.0–1.5 bar. 2) Look for obvious leaks, damp patches or water pooling near the boiler or radiators. 3) Check that radiator thermostatic valves are open and the timer/room thermostat is calling for heat. 4) Inspect the external flue terminal for visible blockages (birds' nests, leaves, snow) and the condensate pipe for signs of freezing in cold weather.

Step-by-step diagnostic and do‑it‑yourself fixes:

1) If pressure is low (below about 1.0 bar): top up using the filling loop according to the boiler handbook until pressure is about 1.0–1.5 bar, then close the valves. After topping up, press the boiler reset button (hold for 5–10 seconds) and see if the 1 red flash clears. If you do not know how to use the filling loop or cannot access it safely, stop and call a professional. 2) Bleed radiators to remove air: work from the lowest radiator up, release trapped air until water flows, recheck system pressure and top up if needed, then reset the boiler. 3) Check for frozen condensate pipe (common in cold weather): if condensate is frozen, thaw the external pipe with warm (not boiling) water or a warm cloth. Turn the boiler off before handling pipes and follow manufacturer guidance, then restart and reset. 4) Check the flue terminal and vents are clear. Blocked flues can affect flow and sensor readings. Clear small visible debris if safe to do so, then reset. 5) Listen for the circulation pump when the boiler is calling for heat: a faint humming is normal. If the pump is noisy, not running or you suspect poor circulation (radiators cold, gurgling or banging), do not open the boiler; call an engineer — pump replacement/repair is a professional task. 6) Perform a single reset: press and hold the reset button for 5–10 seconds and allow the boiler to attempt restart. Do not repeatedly or continuously reset the boiler — if the fault returns more than once, stop and call a Gas Safe engineer.

When to call a professional (Gas Safe engineer):

1) If the 1 red flash persists after the basic checks and reset. 2) If pressure drops repeatedly or there are system leaks. 3) If you suspect a failed sensor, thermistor, PCB, pump, fan or gas valve — these require specialist diagnosis and parts. 4) If you experience ignition faults, overheating, repeated lockouts, strange smells, or any unsafe signs. 5) If you are unsure how to perform the safe steps above.

Final notes:

- The 1 red flash can be a temporary, self-clearing issue, but repeating or persistent faults should always be investigated by a qualified engineer. - Do not continue to reset a boiler that repeatedly faults; this can mask an underlying safety or reliability issue. - Keep a record of when the fault occurred and any steps you took; this helps the engineer diagnose the problem more quickly.