Error 133

Safety first:

1) If you smell gas (rotten egg smell), do not try to reset or investigate the boiler. Turn off gas at the meter if it is safe to do so, leave the building immediately, and call the emergency gas number. Do not use electrical switches or phones inside the building.

2) If you must work near the boiler, switch off the electrical supply to the boiler before touching pipework or the condensate outlet. Do not open the boiler casing or attempt work on gas valves, burners, ignition leads, or the gas circuit unless you are Gas Safe registered.

Initial checks a homeowner can do:

1) Check other gas appliances (hob, gas fire). If they do not work either, you likely have no gas supply — check your meter (pay-as-you-go credit) and contact your gas supplier.

2) Check the gas isolation cock (usually near the gas meter or at the appliance inlet) is in the open position (handle in line with the pipe). Do not force a seized valve.

3) Inspect the external flue outlet (the pipe coming through the outside wall) for obvious blockages such as debris, snow, or bird nests. If blocked, clear only obvious loose debris; do not insert tools into the flue or damage it.

4) Check the condensate pipe (plastic pipe that runs from the bottom of the boiler to a drain outside). In freezing weather this can freeze and block, causing a lockout.

Reset and basic procedure (Baxi GA/EcoBlue style behaviour):

1) Create a demand before reset: turn on a hot tap so the boiler senses a hot water demand (this helps the boiler go through an ignition cycle when you reset).

2) Reset the boiler by pressing and holding the reset/standby button for a few seconds (manufacturer guidance varies; typically 1–5 seconds). The boiler will attempt to relight automatically — it may try up to 5 times before locking out again.

3) If the boiler locks out again and shows E133, do not keep continuously trying resets. Wait about 15 minutes before attempting another reset to avoid unnecessary attempts.

Specific diagnostics and simple fixes you can try:

1) Condensate freeze: If you suspect a frozen condensate pipe, thaw it using warm (not boiling) water poured over the external pipe or by using a hairdryer set to warm. Work safely on a stable ladder if required. Do not use naked flames, boiling water, or aggressive heat. Once thawed, recheck the boiler and reset. Consider insulating or lagging the condensate pipe to prevent re-freezing or fitting a condensate heater/trace cable by an engineer for repeated problems.

2) Flue obstruction: If you saw an obvious external blockage that you safely removed, try a reset. If the flue looks damaged or you cannot safely clear it, stop and call an engineer.

3) Gas supply: If other appliances are working but the boiler still shows E133 after reset, check meter credit and any house isolation valve. If the whole property has lost gas, contact your supplier. If only the boiler seems affected, do not attempt to purge or bleed the gas pipe yourself — call a Gas Safe engineer.

4) Power and wiring: Ensure the boiler has mains power and the display is active. Do not open the case to inspect wiring yourself; if you suspect a wiring or PCB fault, get a qualified engineer.

When to call a professional (Gas Safe engineer/Baxi support):

1) If the reset does not clear the fault after basic checks (gas supply confirmed, condensate thawed, flue clear), call a Gas Safe registered engineer.

2) If you suspect an internal fault (gas valve, ignition electrode, ignition lead, PCB, or if air has entered the gas line and purging is required), this work must only be done by a qualified engineer.

3) If you cannot safely access or clear the condensate pipe or flue, or if the condensate blockage recurs, get a professional to investigate and fit a permanent remedy.

4) If the boiler repeatedly locks out with E133 or the boiler is old and failing frequently, arrange a full service and safety inspection.

Final note: E133 is a safety lockout indicating the boiler cannot safely ignite. Homeowners can reasonably perform the checks listed above (gas supply, meter credit, isolation valve position, flue and condensate external inspection, thawing condensate) and attempt a reset. Anything involving internal gas components, purging, replacement of parts, or unresolved lockouts must be handled by a Gas Safe registered engineer or Baxi technical support.