Error E133

Safety precautions:

- If you smell gas (rotten egg odor) or suspect a leak: do not operate electrical switches, do not light matches, open windows and doors, turn off the gas supply at the meter if it is safe to do so, evacuate the property and call the gas emergency number immediately.

- If you are not confident working near gas appliances do not attempt internal repairs. Only a Gas Safe registered engineer should work on gas valves, regulators, the burner, ignition wiring, or purge the gas circuit.

- Isolate electrical supply to the boiler before accessing internal components. Most homeowner checks do not require opening the boiler casing.

Initial checks a homeowner can do:

1. Check for obvious gas supply loss: try another gas appliance such as a hob. If other gas appliances do not light or have very weak flame, contact your gas supplier. If you have a prepay meter, check credit and top up if needed.

2. Check the gas inlet tap at the meter or service cock is in the open position (handle inline with pipe). If the tap is closed, open it. If it seems seized or damaged, do not force it; call a professional.

3. Inspect the condensate discharge pipe (white plastic pipe running from the boiler to outside) in cold weather. If it looks frozen or solid and frosty, thaw it by pouring warm (not boiling) water over it or wrapping it in warm cloths. Once thawed, insulate the pipe to reduce refreeze risk.

4. Check the flue terminal and air vents outside for visible blockages (birds nests, snow, debris). Remove light obstructions if safe to do so and then reset the boiler.

5. Reset the boiler: ensure the boiler has a demand (run a hot tap so the boiler sees the demand), then press and hold the boiler reset/power button for a few seconds (Baxi guidance varies: typically 1–5 seconds). The boiler will attempt to relight several times. If the fault clears and the flame icon appears, monitor normal operation.

Specific diagnostic and further steps (call an engineer if these do not fix it):

- If reset fails and other gas appliances are working, do not try to adjust internal gas components. The likely causes at this stage are: faulty gas valve or regulator, incorrect gas pressure, ignition electrode or lead failure, PCB/control fault, or air in the gas line. These require CA qualified diagnostic tools and Gas Safe work.

- If you suspect air in the gas circuit (e.g., after gas meter work or running out of gas), the gas circuit may need purging. This must be carried out by a Gas Safe registered engineer.

- If the condensate pipe was frozen and thawing fixed the issue, insulate the exposed length and consider routing changes or trace heating to prevent reoccurrence. If the condensate pipe is blocked by debris rather than frozen, have it cleared.

- If the flue or combustion air supply is blocked and removing the blockage did not help, have an engineer inspect the flue system and perform any required checks or repairs.

- Any evidence of ignition sparking but no gas flow, intermittent flame, or a repeated lockout after reset points to gas valve, regulator, electrode, ignition leads, or PCB faults. Stop attempting DIY repairs and book a Gas Safe registered engineer to diagnose and replace faulty components.

When to call a professional:

- Call a Gas Safe registered engineer if reset and basic external checks (gas supply, condensate thawing, flue clear) do not clear the E133 code.

- Call immediately if you detect a gas smell, if the gas inlet valve appears damaged or seized, or if you are asked to purge the gas circuit.

- Ask the engineer to check gas pressure at the boiler, inspect and test the gas valve, ignition electrode and leads, PCB and controls, and to run any required flue/combustion checks.

Final note: E133 is a safety lockout designed to prevent unsafe combustion. Carry out only the simple external checks listed above. Any work involving gas components, the burner, gas regulator, purging the gas line, or internal wiring must be done by a Gas Safe registered engineer.