Error E133

Safety first: If you smell gas, turn off the gas at the meter, ventilate the area, do not use electrical switches or open flames, and call your gas emergency number immediately. Do not bypass safety interlocks or attempt internal repairs unless you are a qualified gas engineer. Always isolate power before opening the boiler cover and only perform visual checks or non-invasive actions if you are competent.

Initial homeowner checks (safe, non-invasive):

1. Check other gas appliances (hob, fire) to confirm you have a gas supply. If none work, check the gas meter/ECV and, if you have a prepayment meter, ensure it has credit.

2. Check boiler display and attempt a reset per the manual (typically press and hold the Reset button for 1–3 seconds). Wait and observe the boiler as it attempts to light. If the fault clears and stays clear, monitor for recurrence.

3. Check boiler power: ensure the fused spur/switch is on and the consumer unit hasn't tripped.

4. Check boiler pressure on the gauge—typical running pressure is around 1–1.5 bar. If pressure is very low, follow the manual to repressurise before further attempts.

5. In cold weather check any external condensate pipe for freezing. If frozen, carefully thaw with warm (not boiling) water and clear any visible block. Then reset the boiler.

Visual/observational diagnostics you can safely do:

1. With the boiler powered and cover in place, attempt a reset and listen during the ignition sequence. You should hear the ignition spark and gas valve operating. Note if you hear a ticking/spark then gas flow and immediate dropout—this can indicate ignition occurs but the flame is not being detected (rectification).

2. If you are competent with simple continuity checks and only after isolating power, you may inspect external connectors to the ignition electrode and rectification lead for obvious corrosion or loose connections. Do not disconnect gas or internal gas valve components.

When to call a qualified engineer (must-call situations and professional diagnostics):

- If DIY checks do not clear the fault or the boiler repeatedly locks out.

- If you find visible damage to the ignition electrode, ignition leads, or the rectification lead. Replacement or correct positioning of the electrode should be done by a Gas Safe engineer.

- If the gas valve is suspected (valve not opening, incorrect gas pressure at inlet) or there is any sign of gas leak or uncertainty about gas pressure—these require a registered gas engineer.

- If the PCB or flame detection circuitry is suspected (no rectification signal despite good continuity back to electrode), an engineer will need to test and replace control components.

What a professional will do (for your awareness):

- Measure incoming gas pressure and check the gas meter/ECV and supply to the boiler.

- Confirm the gas valve operation and sequence timing.

- Inspect, clean or replace the spark electrode and ignition leads; check and restore correct electrode gap and position.

- Test rectification/flame detection circuit and rectification lead continuity; replace faulty leads or connectors.

- Test PCB behaviour and replace if it is not recognising the flame signal.

Important notes:

- Do not attempt to adjust or replace the gas valve, main burner components, or internal wiring unless you are a qualified gas engineer.

- Do not ignore repeat lockouts; these indicate a persistent safety issue.

- Temporary user fixes (eg. thawing condensate, resetting, replacing a visibly broken external connector) can get a boiler running short-term but should be followed up with a full professional check if the fault reappears.

If the fault persists after the above safe checks, contact a Gas Safe registered engineer and provide them with the E133 code and details of any observations you made (did you hear sparking, did other gas appliances work, was condensate frozen, etc.). This information speeds diagnosis and helps keep the repair safe and effective.