Error E133

Safety precautions:

1) If you smell gas: do not use electrical switches or appliances. Turn off gas at the meter, ventilate the property, leave the building and call the gas emergency number immediately. 2) Isolate power to the boiler before removing covers or touching internal parts. 3) Only perform non-invasive checks yourself. Any intervention on gas valves, pipework, or internal burner components should be left to a qualified Gas Safe engineer.

Initial homeowner checks (safe DIY):

1) Check the obvious gas supply: confirm the gas meter and the boiler isolation valve are open and that other gas appliances (hob, gas fire) work. If no other gas appliances work, contact your gas supplier. 2) Check boiler pressure on the gauge—aim for roughly 1 to 1.5 bar when cold. Re-pressurise using the filling loop if pressure is low and you are confident in doing so. 3) Reset the boiler: follow the manual — typically press and hold the reset button for 1–3 seconds. Wait and listen for ignition. If it clears and runs, monitor for recurrence. 4) Check for a frozen or blocked condensate pipe (common in cold weather). Thaw external condensate pipe with warm (not boiling) water or check for blockages. 5) Look for error pattern: if the boiler fires but then locks out after a short time, that suggests the burner lights but the board is not seeing the flame (rectification/flame sensing issue).

Simple diagnostic and possible minor fixes (do these only with power off where instructed):

1) Observe and listen during a reset: do you hear the gas valve open and a spark/ticking from the ignition area? If there is no spark sound at all, the ignition electrode or ignition supply may be faulty. If there is spark but flame is not detected, suspect the flame sensor/rectification circuit or a poor electrode position/connection. 2) Visual inspection (power off): remove the outer cover and visually inspect the ignition/spark electrode and the small flame sensor lead. Look for obvious damage, heavy corrosion, cracked ceramic, or the electrode bent out of position. If the electrode is just dirty or slightly corroded you may carefully clean the metal tip with fine abrasive very gently and re-fit to correct gap/position. Reconnect and test. 3) Check wiring and connectors: with power off, ensure the connectors to the electrode/rectification lead and the PCB are tight, not burnt, and not broken. Re-seat them. 4) Condensate, flue and air supply: confirm condensate and flue are clear and the air intake is not blocked—these can prevent normal ignition/operation. 5) If you have electrical test skills only: check continuity of the rectification lead and continuity back to the PCB. A lead with intermittent continuity or high resistance can stop the board seeing the flame. Do not attempt to alter the gas valve wiring or internal PCB settings.

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

1) Any confirmed gas supply issues at the meter or if you are unsure about the gas supply. 2) If the fault persists after the basic checks and reset, or if ignition intermittently lights then cuts out. 3) If you find a bent, cracked or seriously corroded electrode that needs replacement — electrode replacement and combustion adjustments should be done by a qualified engineer. 4) If the gas valve, gas pressure, or PCB appears to be the cause — these are specialist repairs. 5) If you smell gas at any point or you cannot safely isolate the appliance.

Notes and reminders:

- Repeated E133 lockouts indicate the boiler’s safety system is doing its job; do not repeatedly force the boiler to run. - Keep records of fault occurrences and any steps you took; this helps the engineer diagnose. - Annual servicing by a Gas Safe engineer reduces the chance of ignition faults. - Never attempt to adjust the gas valve or internal gas components yourself.