E133 Error On Baxi Boiler: Causes & Fixes
The E133 error code is one of the most commonly reported fault codes on Baxi boilers. It signals that the boiler has attempted to ignite but failed to establish or detect a flame — and has locked out as a safety measure as a result. Your heating stops working entirely rather than running poorly, which is the lockout doing exactly what it’s designed to do.
The good news is that many E133 faults have straightforward causes you can check yourself before calling an engineer.
What Does E133 Mean on a Baxi Boiler?
When your Baxi boiler displays E133, it means the ignition sequence has failed. The boiler attempted to fire, couldn’t confirm a flame was established, and shut down safely. This can be triggered by anything from a temporary gas interruption to a worn internal component — so it’s worth working through the checks below before assuming the worst.
Which Baxi Boilers Display the E133 Error Code?
The E133 fault code appears across the Baxi range, including:
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Baxi 600 series
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Baxi 800 series
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Baxi Platinum
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Baxi Duo-tec
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Main Eco Compact
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Main Combi boilers
What Causes the Baxi E133 Error Code?
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Gas supply interrupted — the most common cause; the boiler cannot ignite without a live gas supply
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Frozen condensate pipe — particularly common in cold weather; a blocked condensate pipe triggers an automatic lockout
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Faulty or dirty ignition electrodes — worn or contaminated electrodes produce a weak spark that fails to ignite the burner
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Dirty or faulty flame sensor — the sensor fails to detect the flame even if ignition occurs
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Disconnected electrode lead — the lead connecting the ignition electrode to the PCB can work loose, particularly after recent servicing
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Faulty gas valve — prevents gas reaching the burner even when supply to the property is confirmed
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PCB fault — less common but possible if all other checks draw a blank
How to Fix the Baxi E133 Error Code: Step by Step
Step 1: Check the Gas Supply
Before investigating the boiler, confirm you have a live gas supply. Check whether other gas appliances in your home — hob, gas fire — are working normally. If nothing gas-powered is functioning, the issue is with your supply rather than the boiler. Contact your gas supplier directly.
If you’re on a prepayment meter, check it hasn’t run out of credit — it’s more common than you’d think.
Step 2: Reset the Boiler
A reset clears many E133 faults, particularly where the lockout was caused by a temporary interruption.
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Locate the reset button on the front panel — usually marked with a flame symbol
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Press and hold for approximately 3–5 seconds
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Wait for the boiler to attempt a restart
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If it fires up and the code clears, monitor it for the next hour to make sure the fault doesn’t return
If the E133 comes back immediately or shortly after resetting, there’s an underlying fault present — don’t keep resetting without finding the cause.
Step 3: Check for a Frozen Condensate Pipe
In cold weather, a frozen condensate pipe is one of the most frequent triggers for E133 on Baxi boilers. Check the external plastic condensate pipe — usually white or grey — for signs of ice or blockage.
To thaw it safely:
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Pour warm — not boiling — water along the frozen section
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Alternatively, hold a hot water bottle or heat wrap against the pipe
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Once thawed, reset the boiler
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Insulate the pipe afterwards to prevent a repeat during cold spells
Step 4: Check the Flue and Ventilation
A blocked or obstructed flue prevents safe combustion and can trigger the E133 lockout. Check the external flue terminal for debris, leaves, bird nesting material, or ice buildup. Keeping the flue terminal clear is both a safety requirement and a legal one — never obstruct it.
Step 5: Check Boiler Pressure
Low system pressure can prevent the boiler from igniting safely. Check the pressure gauge on the front of the boiler — it should read between 1 and 1.5 bar when the system is cold. If it’s below 1 bar, repressurise using the filling loop and attempt a reset. If it reads consistently above 2.5 bar, call an engineer before proceeding.
When to Call a Gas Safe Engineer
Stop troubleshooting and call a qualified Gas Safe engineer if:
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The E133 code returns after every reset
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Your gas supply is confirmed working but the boiler still won’t ignite
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The condensate pipe is clear and pressure is correct but the fault persists
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You suspect a faulty ignition electrode, flame sensor, gas valve, or PCB
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The boiler makes unusual sounds during ignition attempts
Gas components, ignition electrodes, and PCB repairs must only be carried out by a Gas Safe registered engineer. Attempting these yourself is both dangerous and illegal.
Frequently Asked Questions
Is the Baxi E133 error code dangerous?
Not immediately — the boiler has locked itself out as a safety precaution rather than continuing to attempt ignition unsafely. However, if the root cause is a gas supply fault or faulty gas valve, do not attempt to investigate gas components yourself. Call a Gas Safe engineer.
Can I fix the Baxi E133 error myself?
You can safely check your gas supply, reset the boiler, thaw a frozen condensate pipe, and check system pressure without professional help. Anything beyond those steps — ignition electrodes, flame sensors, gas valves — requires a Gas Safe registered engineer.
Why does my Baxi boiler keep showing E133 after resetting?
A recurring E133 after every reset points to a persistent underlying fault rather than a temporary interruption. The most likely causes are a faulty ignition electrode, a dirty flame sensor, or a gas valve issue — all of which need a qualified engineer to diagnose and repair properly.
How much does fixing a Baxi E133 error cost?
If it’s a frozen condensate pipe or gas supply issue, the fix costs nothing. An ignition electrode or flame sensor replacement typically costs £80–£200 including labour. A gas valve replacement usually runs between £200 and £400. With a Plus Heat cover plan, parts and labour for boiler repairs are covered — no unexpected bills.
Baxi boiler showing E133 and won’t reset? Call Plus Heat on 0808 164 2892 — our Gas Safe engineers are on hand across the UK, and with a Plus Heat cover plan, boiler faults are covered before they catch you off guard.
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