In This Guide
What does the Baxi E133 fault code mean?
When a Baxi boiler fires, it runs a controlled ignition sequence: the gas valve opens, the ignition electrode sparks, and a flame-sensing electrode confirms that a stable flame has established. E133 appears when that flame is not detected after several attempts. The boiler treats this as an ignition failure and locks out, shutting off the gas so it cannot keep releasing it without a confirmed burn.
E133 shows up across the Baxi range, including the 600 and 800 series, Platinum and Duo-tec models. In most cases it points to a gas supply problem, which is also the part you can check quickly yourself. Less often it is a hardware fault in the ignition or flame-detection system. Either way it is a lockout, so the boiler will not fire again until it has been reset and the underlying reason has been dealt with.
Is a Baxi E133 fault dangerous?
On its own, E133 is the safety system working as intended. The boiler has cut the gas rather than keep attempting to light without a confirmed flame, which is exactly what it should do. It is not, in itself, a gas emergency.
There is one important exception. If you can smell gas at any point, do not attempt a reset. Leave the property, open a window or door if it is safe to do so, and call the National Gas Emergency Service on 0800 111 999. Otherwise, the main risk with E133 is the temptation to keep resetting it. Clearing the code repeatedly without fixing the cause simply masks a real fault and delays the repair, so limit yourself to a single reset.
What causes a Baxi E133 fault?
Ignition failure comes down to gas reaching the burner, a spark lighting it, and the flame being detected. The table below sets out the usual causes and who should deal with each.
|
Cause |
What is happening |
Who resolves it |
|
Gas supply interruption |
No gas, or too little, reaches the burner so it cannot light |
You can check the basics; your supplier for wider issues |
|
Frozen condensate pipe |
In cold weather a blocked condensate pipe forces the boiler into lockout |
You can often thaw it; an engineer if unsure |
|
Dirty or worn ignition electrode |
A weak or missing spark means the burner never lights |
Gas Safe engineer |
|
Dirty or worn flame-sensing electrode |
The flame lights but the sensor cannot read it, so the boiler assumes failure |
Gas Safe engineer |
|
Faulty gas valve |
Gas is not delivered correctly to the burner |
Gas Safe engineer |
|
Fan fault or blocked flue |
Disrupted airflow prevents safe, stable combustion |
Gas Safe engineer |
|
PCB fault (rare) |
The control board misreads the ignition or flame signal |
Gas Safe engineer |
By far the most common trigger is a gas supply issue, whether that is an empty prepayment meter, a gas valve turned off, an LPG tank running low, or a wider supply interruption. On a boiler that has been in service for several years, ageing ignition and flame-sensing electrodes are the next most likely culprits, because they sit in the harshest part of the boiler and foul or wear over time. Frozen condensate pipes are a seasonal spike and are usually the easiest of all to clear.
What you can safely check before calling an engineer
A few checks are safe for any homeowner and will often either clear an E133 fault or tell the engineer exactly where to look.
Start with your gas supply. Check whether your other gas appliances, such as a hob, oven or gas fire, are working. If they are not, the problem is your gas supply rather than the boiler, so contact your supplier. If you are on a prepayment meter, check you have credit and that the supply is switched on, and make sure the gas service valve on the boiler pipework has not been knocked closed.
Next, if it is cold outside, check the condensate pipe. This is the plastic pipe, usually white, that runs from the boiler to an outside drain. In freezing weather it can block with ice and trip the boiler. Thawing it gently with warm, not boiling, water poured along the exposed section will often clear the fault. Take care on steps or ladders in icy conditions.
Finally, reset the boiler once, following the instructions in your Baxi manual. If it fires and holds, keep an eye on it. If E133 returns, stop there. Do not open the boiler casing or touch any internal parts. Anything involving the gas valve, electrodes, fan or wiring is gas work and must be left to a registered engineer.
When to call a Gas Safe engineer
If the reset does not hold, if E133 keeps returning, or if your gas supply is clearly fine, the fault is almost certainly internal and needs professional diagnosis. Ignition electrodes, flame-sensing electrodes, gas valves, fans and control boards are not homeowner repairs. By law, any work on the gas side of a boiler must be carried out by a Gas Safe registered engineer, both for your safety and to keep the boiler’s warranty intact. Every 0800 Homefix engineer is Gas Safe registered.
If your Baxi is also showing other codes, it can help to read across them. Our guides to the Baxi E160 fan fault, the Baxi E119 low pressure fault and the Baxi E125 fault cover the codes that most often appear alongside an ignition lockout.
How 0800 Homefix fixes a Baxi E133 fault
When we attend an E133 fault, the engineer works through the ignition path in order: confirming the incoming gas supply and pressure, checking the ignition and flame-sensing electrodes and their leads, testing the gas valve, checking the fan and flue for restriction, and reading the PCB diagnostics where needed. Diagnosing in that sequence means we find the true cause rather than swapping parts on a guess.
We charge for the first hour’s labour, paid in advance, which covers the engineer’s visit and the diagnosis. If further work or a part is needed, we confirm the cost with you and agree it before any repair begins, so there are no surprises. Full details are on our rates page. Our labour is guaranteed for 12 months, and any manufacturer part we fit is covered by the manufacturer’s own 12-month guarantee.
We cover London and the South East, seven days a week, 365 days a year. If your Baxi is locked out on E133 and a single reset has not cleared it, our boiler repair team can get your heating and hot water back safely.
Helpful resources
To confirm that any engineer working on your boiler is qualified, you can check them on the Gas Safe Register. For model-specific guidance and manuals, Baxi’s help and advice pages cover the fault codes for each boiler in their range.
Frequently Asked Questions
What does E133 mean on a Baxi boiler?
E133 means ignition failure. The boiler tried to fire but no flame was detected after several attempts, so it locked out and shut off the gas. It will not fire again until it is reset and the reason it failed to light has been resolved.
How do I reset a Baxi boiler after an E133 fault?
Why does my Baxi keep showing E133?
A reset only clears the code, it does not repair anything. If E133 returns, something is still stopping the boiler from lighting and confirming a flame, most often a gas supply problem, a worn ignition or flame-sensing electrode, or a faulty gas valve. These need an engineer to diagnose and fix.
Can I fix a Baxi E133 fault myself?
You can carry out the safe checks: confirm your other gas appliances work, check prepayment credit and the gas service valve, thaw a frozen condensate pipe in cold weather, and reset the boiler once. If E133 returns, the cause is internal and needs a Gas Safe registered engineer. Never open the boiler or work on the gas components yourself.
Is E133 a gas supply problem or a boiler fault?
It can be either. The most common cause is a gas supply issue you can check yourself, such as an empty meter or a closed valve. If the supply is fine, the fault is usually internal, such as a worn electrode or a faulty gas valve, which an engineer will diagnose.
Still Locked Out on E133?
If your Baxi has locked out on E133 and a single reset has not brought it back, book an 0800 Homefix Gas Safe engineer. We cover London and the South East, seven days a week, and diagnose the ignition fault properly before any repair, so you are only paying to fix the real cause. Book online or through our boiler repair page to arrange a visit.
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Editorial note: This article is intended as a general homeowner guide. All plumbing work on supply pipes should be carried out by a qualified, WaterSafe-registered plumber. If you suspect a gas leak, leave the property immediately and call the National Gas Emergency Service on 0800 111 999.
