Error E133

Safety precautions:

1) If you smell gas (rotten egg odour), do not operate electrical switches, do not light matches, open doors and windows, get everyone out of the building and call your national gas emergency number immediately. 2) If you are unsure about any step below, stop and call a Gas Safe registered engineer. 3) Do not attempt to work on the gas supply, gas valve, PCB, or internal ignition components unless you are a qualified gas engineer.

Initial checks a homeowner can do:

1) Reset the boiler once: for GA-range Baxi boilers press and hold the standby/reset button for around 1–3 seconds (some Baxi models use 2–5 seconds). The boiler will attempt to relight (the boiler may make up to five ignition attempts before locking out again). If the fault clears and a flame symbol appears, monitor operation. Do not repeatedly reset — after repeated failed attempts the boiler may lock out and require a waiting period before reset. 2) Check gas supply: test another gas appliance (hob, gas fire) to confirm the house has gas. If you have a prepay meter, check credit. Locate the gas meter and the gas service cock — the handle should be in line with the pipe for open. If you suspect a wider supply issue, contact your gas supplier. 3) Inspect the condensate pipe: in cold weather the external 21–22mm plastic condensate discharge pipe can freeze. Locate the external condensate pipe and look for frost or blockages. Thawing (if you are confident to do so) can often restore operation — use warm (not boiling) water poured along the frozen section or use a hairdryer on low heat; never use open flame or sharp tools. After thawing, reset the boiler. 4) Check the flue/vent: look at the external flue terminal for obvious blockages such as bird nests, snow or debris and clear only if safe to do so. Ensure intake air/ventilation openings are not blocked.

Specific diagnostic and fix steps (homeowner-friendly vs engineer-only):

Homeowner steps you may safely follow:

- Perform the single reset as described above and observe whether the boiler attempts to ignite and whether the flame symbol appears. Wait and do not keep resetting if it does not start.

- Confirm other gas appliances work and the meter/cock is on. If other appliances are also not working, contact your gas supplier before calling an engineer.

- Thaw and insulate the condensate pipe outside; after thawing, insulate it with foam pipe insulation or trace heating where practical to prevent re-freezing.

- Clear obvious external flue obstructions if accessible and safe.

Actions that must be done by a Gas Safe registered engineer (do not attempt yourself):

- Checking and measuring gas working pressure (Baxi guidance typically looks for around 18 mbar or higher at high fire on certain models) and adjusting or replacing the gas regulator/valve if required.

- Purging air from the gas line or re-pressurising a bottled LPG system.

- Inspecting, cleaning, adjusting or replacing ignition electrodes, inspecting electrode leads, checking spark gap and securing earth tags.

- Draining water from the heat exchanger or condensate traps if condensate has back-filled the combustion chamber and affected the electrodes.

- Diagnosing PCB, gas valve faults, or smoke/combustion anomalies and performing automatic calibration procedures where applicable.

When to call a professional:

1) If the boiler will not restart after the basic checks (reset, gas supply check, thawing condensate, clearing flue) or the E133 returns repeatedly. 2) If you cannot confirm the gas supply or other gas appliances are also affected. 3) If you detect water inside the combustion chamber, persistent internal faults, or any electrical or gas component issues. 4) If you smell gas — this is an emergency.

Provide the engineer with the following information where possible: the exact error code (E133), what you have already tried (reset, thawed condensate, checked meter/hob, cleared flue), whether other gas appliances work, and how long the fault has been present. A Gas Safe engineer will have the tools to test gas pressure, check ignition components and the condensate/drainage system, purge air if needed, and replace faulty gas or ignition parts safely.