Error E133

Safety precautions:

- If you smell gas (rotten egg odour), get everyone out, do not use phones or switches inside the building, call the emergency gas number and your gas supplier from a safe location.

- Do not attempt internal gas or combustion-system repairs unless you are a Gas Safe registered engineer.

- Do not use open flames or hot water above warm to thaw frozen plastic pipes; never use a blowtorch.

- Follow manufacturer instructions for resetting (consult your boiler manual if unsure).

Initial checks a homeowner can do:

1. Confirm other gas appliances work: try a gas hob or gas fire. If none of them work, the problem is likely a supply issue — check prepay meter credit if applicable and contact your gas supplier if necessary.

2. Check the gas isolation tap to the boiler (near the meter or at the appliance). The tap should be inline with the pipe. Only operate this if you are confident and familiar with it.

3. Power and call for heat: ensure the boiler has power and there is a genuine hot water or heating demand (turn on a hot tap) before attempting a reset.

4. Reset the boiler: locate the boiler reset/power button and press and hold as the manual recommends (many Baxi models use press-and-hold for around 1–5 seconds). The boiler will then attempt to relight — it may try up to five times before locking out again. If E133 clears and the flame symbol appears, observe normal operation.

5. Check the condensate pipe: in cold weather the external white condensate pipe can freeze. If the external pipe is hard/frosty, thaw it by pouring warm (not boiling) water over the frozen section or use a hair dryer; wear gloves and protect surfaces. After thawing, reset the boiler. Do not use boiling water or open flame.

6. Inspect the flue externally: look at the flue terminal outside for obvious blockages (leaves, snow, bird nest). If you can safely and easily remove debris without risking a fall, do so; otherwise leave it for an engineer.

If the error returns after initial checks:

1. Do not repeatedly try to force restarts. Many Baxi boilers will auto-lockout after five failed ignition attempts and then require 15 minutes before another reset can be accepted.

2. Check for visible water around the ignition area only if you are competent and the boiler is isolated from power and gas. A simpler homeowner action is to look for signs of leakage around the condensate connection under the boiler. If you find water in the combustion area or suspect a blocked condensate trap, call an engineer — draining combustion chamber water and removing blockages is best left to professionals.

3. Do not attempt gas pressure measurement or purging. Low or incorrect gas pressure, a faulty gas regulator or a blocked gas valve are common causes and require specialised test equipment and Gas Safe competence to diagnose and fix.

4. Ignition electrode and wiring: you can visually check the spark lead is connected and not obviously damaged. Do not dismantle electrodes or adjust spark gaps unless you are a qualified engineer. Moisture or a faulty electrode can prevent ignition and will need an engineer to inspect and correct.

When to call a professional (Gas Safe registered engineer):

- The boiler will not reset or E133 returns after the basic checks and thawing the condensate pipe.

- You cannot restore gas supply to the house or multiple gas appliances are dead — contact your supplier or engineer.

- Smell of gas, persistent leaks, suspected faulty gas valve, regulator, low gas pressure or need to purge the gas circuit.

- Water found inside the combustion chamber, blocked internal condensate drainage, ignition electrode replacement, PCB or gas-valve faults, or any work requiring gas isolation and re-commissioning.

What the engineer will likely do:

- Measure gas working pressure at the boiler and at the test point and check for supply faults.

- Inspect and, if needed, clean/replace ignition electrodes and leads, check spark gap and electrode earth, and test the ignition sequence.

- Clear or replace condensate trap/pipe and drain any water from the heat exchanger if necessary.

- Check the flue for safe operation and any smoke recirculation/calibration issues and carry out automatic calibration if required.

- Repair or replace faulty gas valves, regulators or electronic control components and re-commission safely.

Final note: E133 is a safety lockout indicating ignition or gas delivery problems. Start with the simple checks above (gas supply, condensate pipe thaw, reset, flue clear) but do not attempt gas-side repairs or internal component fixes yourself. Contact a Gas Safe registered engineer if the fault persists or if any gas-side work is needed.