How to Fix Main E133 Fault Code (UK)
Main showing E133 — Ignition failure. UK diagnosis, likely spare (electrode 720301101) and step-by-step reset.
Main
What the code means
E133 on a Main indicates ignition failure. The boiler locks out to protect the heat exchanger and, on gas faults, to comply with the Gas Safety (Installation and Use) Regulations. Always reset to confirm the code is live, not historical.
Likely spare
The most common fix is the electrode 720301101. Check the exploded diagram against the GC number on the data plate before ordering — Main revised parts on Main units mid-production.
Fix procedure
Baxi group PCB — same fault tree.
Log the fault and reset. If the code returns within 24 hours, escalate to full electrical diagnosis with a manometer and multimeter.
Frequently asked questions
- Can I reset E133 myself?
- You can press the reset button up to 3 times. If E133 returns, the boiler needs a Gas Safe engineer — it is illegal to repair gas components without registration.
- Is the part covered under warranty?
- Main standard warranty is 2–10 years depending on model. Registered installations get the full term. Check the sticker inside the case.
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