Error E129

Safety first:

1) If you smell gas: do not touch the boiler. Turn off gas at the meter if you can safely do so, ventilate the area, leave the property, and call the gas emergency number immediately.

2) If there are signs of carbon monoxide (headache, nausea, soot, yellow burner flame) turn off the boiler, ventilate and call an engineer immediately.

3) Do not repeatedly reset the boiler more than 2-3 times. Repeated resets can mask a real fault and are unsafe.

Initial homeowner checks you can do (no internal access):

1) Check the display and note the exact code and any additional messages or number of ignition attempts.

2) Try a single reset: follow the boiler handbook reset procedure (usually press and hold the reset button or selector for 5–10 seconds). Wait to see if the boiler completes the ignition sequence and holds the flame.

3) Check mains power to the boiler and any external time/temperature controls. Ensure the boiler has power and is calling for heat or hot water when you test.

4) Check the gas supply: confirm other gas appliances work, the gas meter is on and (if on prepay) has credit. If you suspect a gas supply interruption, call your gas supplier.

5) Check the external flue, air vents and terminal for obstructions (birds' nests, debris). Also inspect the condensate pipe if it runs outside—if frozen, thaw with warm (not boiling) water.

6) Check boiler pressure gauge: while E129 is a flame issue, very low pressure or dry system can produce unusual behaviour; top up if pressure is below the recommended level (refer to your manual) but only if you know how to use the filling loop safely.

If the fault persists after initial checks:

1) Record what you observed: exact error code, number of resets, whether it fails on cold start or after running, any unusual noises or smells. This information helps the engineer.

2) Avoid opening the boiler casing or touching burner components if you are not qualified. Internal checks involve live gas parts, ignition electrodes and flame detection circuits which present real danger.

3) Possible professional diagnostics (for a Gas Safe engineer): check gas pressure at the inlet, inspect and test ignition electrode and flame sensor (ionisation probe), check burner and injector condition, inspect wiring and connectors for corrosion, check PCB and valve operation, and examine flue and condensate route for faults. They will also check for stored fault history and perform safe ignition tests.

When to call a professional:

1) If the error does not clear after one reset and the simple external checks above.

2) If you hear ignition sparks but no flame, or if the flame lights then immediately extinguishes.

3) If gas supply and vents are fine but the boiler still locks out, or if you are uncomfortable performing the basic checks.

Provide the engineer with the model (Baxi GA range), the E129 code, any other codes shown, and details of what you have already tried. Do not attempt repairs to gas valves, burners, ignition electrodes, or internal wiring yourself. A Gas Safe registered engineer should carry out any internal inspection and repair to ensure safety and compliance.