Baxi E133 Error Code: Meaning and How to Fix It

The Baxi E133 error code means the boiler tried to light but could not, and Baxi lists it as a gas supply fault on many of its gas boilers. Baxi’s own help pages link E133 to three things: the gas supply, the ignition and flame sensing, or a blocked or frozen condensate pipe.

Quick answer: E133 on a Baxi boiler is a gas supply or ignition lockout. Check other gas appliances work and any prepayment meter has credit, and in freezing weather thaw the condensate pipe with warm, not boiling, water. Then reset the boiler. If E133 keeps returning, call a Gas Safe registered engineer.

What Does the Baxi E133 Error Code Mean?

E133 means the boiler did not detect a flame when it tried to light, so it has locked out.

On Baxi’s boiler error codes table, E133 is a “Gas supply fault”, with the advice to check the power supply, sensing electrode, spark electrode and cable. Baxi’s reset guide describes E133 as a problem with the gas supply, ignition and flame, or a blocked condensate. Its frequently asked questions add that E133 can mean the condensate pipe is frozen, because a blocked condensate stops the boiler firing.

Baxi lists E133 for these ranges: Platinum, Platinum Compact and Platinum+ combis, Duo-tec and Duo-tec Compact combis, Megaflo and Megaflo Compact system boilers, Baxi 600 and 800 combi and system, Assure, EcoBlue, Main Eco Compact and Potterton Assure. Newer Baxi 200, 400, 600 and 800 Combi 2 and System 2 boilers use a different code format, such as E.01.04 for “flame loss detected five times in 24 hours”, so check your model’s manual.

What Causes the E133 Error?

Most E133 lockouts come from the gas supply or, in cold snaps, a frozen condensate pipe. Faulty parts come next.

• No gas reaching the boiler: a prepayment meter out of credit, a supply interruption, or a closed gas valve after other work.
• Frozen condensate pipe: Baxi says E133 can mean a frozen condensate pipe, usually where the pipe runs outside and is most exposed.
• Power supply problem: Baxi’s table lists checking the power supply first.
• Sensing or spark electrode fault: a worn, dirty or badly placed electrode cannot light the burner or detect the flame.
• Damaged ignition cable: Baxi names the cable alongside the electrodes.

How Do You Fix the E133 Error Yourself?

A homeowner can check the gas supply, thaw a frozen condensate pipe and reset the boiler. Work through the steps in this order.

1. Check for a gas smell. If you smell gas, do not reset. Follow the emergency steps in the safety box below.
2. Test another gas appliance. If a gas hob will not light either, the problem is your supply. On a prepayment meter, check for credit and top up.
3. In freezing weather, check the condensate pipe. This is the plastic pipe that runs from the boiler to a drain, often outside. Baxi’s steps are:
   a. Switch the boiler off at the control panel and turn off the electricity at the wall.
   b. Find the frozen section, usually the most exposed part.
   c. Warm the pipe along its exposed length with a hot water bottle, a microwaveable heat pack or warm water from a watering can.
   d. Never use boiling water straight from the kettle, as Baxi warns it could damage the pipe.
   e. Turn the power back on and restart the boiler, repeating if needed.
4. Reset the boiler. Baxi describes three methods: press the reset button until the red light goes out; or turn the temperature knob fully anticlockwise and hold until the lockout light goes out, then turn it back; or turn the selector switch to R and hold for at least 5 seconds.
5. Watch it relight. If the boiler fires and runs, the cause was probably the supply or the condensate. If E133 returns straight away, go to the next section.

Safety: Stop if E133 returns after a reset with the gas supply working and the condensate clear. Do not remove the casing or touch the electrodes, ignition cable or gas valve. HSE says anyone employed to work on gas appliances in a home must be a Gas Safe registered engineer. If you smell gas, open windows, avoid switches and naked flames, leave the building and call the National Gas Emergency Service on 0800 111 999.

When Should You Call an Engineer?

Call a Gas Safe registered engineer if E133 returns once your gas supply is confirmed and the condensate pipe is clear. Baxi’s own reset guide says that if lockout occurs frequently, a fault is indicated and you should contact your installer or service engineer.

The remaining causes on Baxi’s list, the electrodes, the ignition cable and the gas valve, are all inside the sealed casing. The Health and Safety Executive is clear that work on domestic gas appliances must be done by a Gas Safe registered engineer. Give the engineer your boiler model, how often E133 appears, and whether it happens mainly in cold weather.

Baxi Codes Related to E133

These codes come from the same Baxi table that lists E133, so they apply to the same boiler ranges.

For a low pressure code such as E118, our guide on how to repressurise a combi boiler walks through the filling loop safely.

How Can You Stop the E133 Error Coming Back?

Preventing E133 means protecting the gas supply and the condensate pipe, and servicing the boiler.

• Service the boiler every year. HSE advises that gas appliances, flues and pipework are serviced at least annually by a Gas Safe registered engineer, who can inspect the electrodes.
• Ask about the condensate pipe. If E133 appears in every cold snap, ask your engineer whether the external condensate pipe can be rerouted or insulated.
• Keep a prepayment meter in credit through winter. The gas bill calculator converts meter readings into kWh and cost so you can plan top ups.
• Plan for an old boiler. If a boiler keeps locking out despite repairs, the boiler size calculator gives a guide kW range for comparing replacement quotes.

Baxi E133 Error Code FAQs

Checked October 2026. Sources: Baxi, Boiler error codes, Baxi, How to reset a Baxi boiler, Baxi, What do Baxi error codes E23, E53, E133, E119 and E128 mean?, HSE, Domestic gas: frequently asked questions.