Error 4 flashes 5 seconds off

Safety first: if you smell gas, do not operate the boiler, do not switch electrical items on or off, ventilate the area, turn off the gas supply at the meter and call the gas emergency number. Before doing anything else, isolate mains power to the boiler if instructed by your gas engineer and never attempt to work on gas, ignition electrodes, gas valves or the PCB yourself. Only undertake external visual checks and non-intrusive actions.

Initial homeowner checks you can do:

1) Reset the boiler: many Worcester boilers require pressing the reset or spanner/return button for about 3 seconds, or turning the control knob anti-clockwise to the reset position. Try a single reset and observe if the boiler attempts to light and whether the same fault returns. Do not repeatedly reset more than a couple of times.

2) Check mains power and display: ensure the boiler has power and the boiler pressure is in the normal range (typically around 1–1.5 bar when cold). If the boiler is without power or the pressure is very low, address those issues first (restore power, repressurise following the manual) and then try a reset.

3) Check gas supply: confirm other gas appliances (hob, gas fire) work to rule out a house gas supply problem. Ensure the gas isolation valve to the boiler is fully open.

4) Check for obvious external faults: look at the flue termination outside for blockages (nests, debris), check the area around the boiler for signs of water ingress or corrosion, and ensure vents and combustion air paths are clear.

5) Check for frozen/blocked condensate pipe in very cold weather (if visible outside) as this can cause lockouts on some boilers; thaw it carefully if you suspect freezing.

6) Record information: note the exact fault sequence, any additional long-flash codes, and the cause code from the information menu (press the spanner/return button) if your boiler shows one. Take a photo of the fault display and the spanners/codes for the engineer.

Specific diagnostic and safe next steps:

1) After the above checks, attempt one reset and observe closely: listen for fan start, spark/ignition noise, and whether the boiler attempts to light. If the boiler sparks but flame is not detected, this suggests an ionisation/flame detection problem or gas supply issue. If there is no spark at all, the ignition module or electrode may be at fault.

2) Do not open the boiler case to inspect or touch the ignition electrode, gas valve, or wiring. Do not attempt to clean or adjust the electrode yourself; the electrode position and insulation are critical for safe operation.

3) If the fault reoccurs immediately or the boiler will not light after the checks, turn the boiler off and contact a Gas Safe registered engineer. Provide them with the exact flash code sequence, any cause code from the information menu, what checks you have already done, and photos if possible.

4) When to call urgently: persistent lockouts, repeated ignition failures, smell of gas, visible damage, or if other gas appliances are affected. For recurring ignition timing errors, expect the engineer to check the ignition electrode and lead, flame sensing circuit (ionisation), gas valve operation, gas supply pressure, fan and airflow, and the boiler control electronics.

Final note: this is a gas ignition safety fault and should not be repaired by an unqualified person. A Gas Safe registered engineer should do diagnosis and any repairs involving gas, ignition components, or internal wiring. Follow the engineer’s advice and ensure the boiler is fully tested and commissioning checks are completed before returning it to normal service.