Error E128

Safety precautions:

- If you smell gas, do not operate any electrical switches, do not light matches or naked flames. Evacuate the property immediately and call the national gas emergency service.

- Turn off the boiler’s electrical supply and gas supply only if you know how and it is safe to do so. If unsure, leave supplies alone and call a Gas‑Safe engineer.

- Never try to adjust, disassemble or replace gas components, the burner, the ignition electrode or PCB yourself. Those tasks require a Gas‑Safe qualified professional.

Initial homeowner checks you can safely do:

1) Note the exact error code and any other codes or LED behaviour; record how many times the fault has occurred and whether the boiler is locked out.

2) Try a single reset of the boiler using the reset button (hold 3–5 seconds). If the boiler resets and runs normally for a period, monitor it — persistent recurrence indicates a professional call is needed.

3) Check the household gas supply: see whether other gas appliances (cooker, gas fire) operate. If other gas appliances don’t work either, the issue may be with the gas supply or meter—call your gas supplier.

4) Check boiler and system pressure at the gauge. If pressure is very low (<1.0 bar) top up to the recommended level (usually around 1.0–1.5 bar) following the manufacturer’s instructions, then reset and re-check.

5) Inspect visible external parts: flue terminal (outside) for obvious blockages or bird nests, and the condensate pipe in cold weather for signs of freezing. Also listen for unusual fan noises during start-up.

Diagnostic and next-step actions (homeowner-friendly, non-intrusive):

1) If the condensate pipe is frozen, thaw it safely with warm (not boiling) water or towels and re-check the boiler. A frozen condensate can create faults that prevent correct combustion.

2) If the flue terminal looks blocked or obstructed, clear only superficial debris that is safely accessible from ground level. Do not climb onto roofs; call an engineer for flue checks if unsure.

3) After topping up pressure and clearing any obvious external blockages, reset the boiler once. If the E128 returns immediately or after a short time, do not keep resetting repeatedly — repeated resets can mask a developing safety issue and will normally lead to lockout.

4) If other gas appliances are working and external checks are clear but the E128 persists, make a note of when the fault happens (heat demand, hot water only, cold start, after a period running) and any sounds or smells. This information helps the engineer diagnose intermittent faults.

When to call a professional and what to tell them:

- Call a Gas‑Safe registered engineer if the fault returns after a single reset, if the boiler goes into lockout repeatedly, if you see signs of burner instability (popping, unusual smells), or if any internal boiler components are suspected.

- Do not attempt to clean or replace the flame electrode, remove burner covers, or adjust gas pressure yourself. These are gas‑regulated tasks.

- When you contact the engineer, provide model, serial number, the E128 code, the number of lockouts, what initial checks you performed, system pressure reading, whether other gas appliances are working, and whether you detected any unusual noises or smells.

Likely professional diagnostic steps (what the engineer will do):

- Confirm gas supply and pressure to the boiler and test for interruptions or poor pressure.

- Inspect flame detection electrode (ionisation probe) and ignition components; clean or replace if worn or contaminated.

- Check and test the gas valve operation, gas valve wiring and mains supply to the boiler.

- Run combustion checks and check fan and air pressure switch to ensure correct air/gas mixture and no flue/airflow restrictions.

- Test PCB and ignition module; replace if intermittent faults or faults recorded in fault log.

- Check for and remedy any flue or condensate issues that may affect operation.

Final note: E128 is a safety-related flame failure fault. Small initial checks and a single reset are reasonable for a homeowner, but anything involving the gas train, flame sensing, ignition or PCB must be left to a Gas‑Safe registered engineer. If in doubt, isolate the boiler and arrange an emergency service visit.