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Safety precautions:

1) If you smell gas: stop using gas appliances, do not operate electrical switches, open windows and doors, leave the building and call the gas emergency number and/or your local emergency services. Do not attempt internal repairs.

2) If you are unsure or uncomfortable at any point, stop and call a Gas Safe registered engineer. Do not remove sealed covers or work on gas or electrical components.

3) Limit resets: do one short reset attempt only. Repeated resets mask underlying faults and can cause further lockouts.

Initial checks a homeowner can safely do:

1) Check the programmer/room thermostat: ensure the boiler is set to provide heating or hot water and that any timers or external controls are calling for heat. Increase the set temperature to confirm a demand.

2) Check the boiler power: ensure the boiler is switched on at the isolator and that any external fused spur has not tripped. Try turning the boiler off at the isolator for 30 seconds and then back on to perform a basic reset.

3) Note the indicator lights and behaviour: is the blue power LED on? Is the green burner LED on, off or flashing? Count any flashes or pulses and write them down — these help a technician diagnose the fault.

4) Check system water pressure: look at the pressure gauge. Ideal resting pressure is about 1–1.5 bar. If below about 0.8 bar, the boiler may refuse to fire. If low, you can top the system up using the filling loop: open the filling valves slowly until pressure reaches about 1.0–1.5 bar, then close the valves. Refer to your boiler manual for the specific filling-loop procedure for your model.

5) Check for visible leaks or discharged PRV pipework: look for water under the boiler, wet PRV discharge outside, or leaking radiator valves. If you see a leak or the PRV is discharging, switch the boiler off and call an engineer.

6) Check the condensate discharge (if applicable): in cold weather the condensate pipe can freeze. If you suspect freezing, gently thaw the external section with warm (not boiling) water or a warm towel. Clear visible blockages. If thawing restores operation, monitor the pipe and insulate/replace as required by an engineer.

7) Confirm gas supply at the meter or other gas appliances (only if safe to do so): check if a gas hob or other gas appliance works. If multiple gas appliances have no supply, contact the gas supplier. If you suspect a gas issue, call the gas emergency number.

Specific diagnostic and next-step fixes:

1) Power-cycle and single reset: with the boiler powered, press the reset once following the manual instructions. Listen for fan/pump operation and any attempts to ignite. If the boiler starts and continues working, monitor for reoccurrence. If it locks out again, note when and how (after X seconds, flashing pattern, noises).

2) If the pump or fan runs but there is no ignition: this typically points to gas supply/valve or ignition electrode problems, or a safety sensor/PCB issue. Do not attempt to adjust or replace these parts yourself — call a Gas Safe engineer.

3) If the boiler is in service mode or a special mode (siphon fill, minimum/maximum mode, temperature blocking): some Ri boilers show particular lights when in one of these built-in modes. If the boiler was recently serviced, check that any service switch has been returned to normal. If a mode message says to wait (eg siphon fill or air purge) allow up to 15–30 minutes; if it persists, contact service.

4) If topping up pressure fixed the problem and it does not drop again, continue to monitor. If pressure keeps falling after topping up, there is a leak or a faulty component (e.g. expansion vessel or PRV) — call an engineer.

5) If a frozen/blocked condensate pipe was cleared and the boiler now fires, insulate the pipe or arrange a permanent repair with a technician to prevent repeat faults.

6) If the control LEDs are on but the boiler does nothing and you suspect LED/PCB failure (for example the boiler works but the indicator is not behaving as expected), this can indicate a control-board or connection fault. Record the symptom and contact an accredited engineer — PCB repair or replacement should only be done by a qualified technician.

When to call a professional:

1) Call a Gas Safe registered engineer if the boiler still will not fire after the basic checks above, if you smell gas, if there are repeated lockouts, visible leaks, PRV discharge, or if you are unsure how to proceed.

2) Give the engineer the boiler model, serial number, a clear description of the lights/flash pattern, what you have already tried (pressure topped up, condensate thawed, reset performed) and any noises heard. This speeds diagnosis.

3) Faults involving the gas valve, ignition electrode, sensors, fan motor, pump, PCB or internal wiring must be inspected and repaired by a Gas Safe engineer.

Final note: do not attempt internal repairs on gas or electrical components. Use the safe checks above to narrow down simple causes, but arrange professional service for any persistent, repeated, or safety-related faults.