How to Fix an E133 Baxi Boiler Fault: Error Repair Guide

Last updated on January 11th, 2025

The E133 Baxi fault code is shown on the boiler display when there is a problem and your boiler goes to lockout. I have been carrying out boiler repairs full-time for over a decade and having fault codes on the screen when I arrive is very welcome. Here I’ll show you some ways to fix a Baxi boiler with an E133 fault based on my on-the-job experiences.

What does E133 mean?

This error code is also used on Main and Potterton boilers (Baxi-owned). The Baxi, Main and Potterton E133 faults are the same.

E133 fault meaning from a Baxi manual:

E133 indicates that the gas supply has been interrupted, ignition has failed or the flame has not been detected.

– Baxi

Some common causes:

• Gas supply fault: The boiler has been locked out due to not getting any or enough gas. This can be checked quite easily without having to open up the boiler
• Frozen condensate pipe: If it’s below zero cold weather and you have an external condensate pipe, there is a good chance it has frozen causing your boiler to lockout
• Leak in combustion chamber: The flame sensing electrode cable can get wet if there’s a leak in the combustion chamber
• Faulty boiler parts: Boiler parts often fail and need to be replaced

How to fix an E133 fault

The first thing I would check is that the gas is turned on at the gas meter emergency control valve (ECV).

Gas supply fault

If you have other gas appliances, like a gas hob or gas fire, check to see if these are working to find out if you are getting gas in the property. Prepay gas meter: If you have a prepayment gas meter, make sure you are in credit as this is a common situation I come across.

Frozen condensate pipe

If it’s freezing outside, having a frozen condensate pipe is possible. You can pour hot water on it to melt the frozen water inside the pipe and reset the boiler. Your condensate pipe could also be blocked if it’s not freezing weather.

Leak in combustion chamber

A leak inside the combustion chamber on certain Baxi boilers (Duo-Tec, Platinum…) will cause a pool of water to fill the bottom. The flame sensing electrode cable connector sits in this water which causes the boiler to cut out a second or two after firing up. This is an easy fix for a gas engineer.

The cable must be lifted out of the water, disconnected, and any water blown out of the connectors. Then, the cable must be rerouted slightly (to keep it off the bottom permanently) and reconnected. The boiler will now work again, but the leak needs to be found and fixed.

Faulty boiler parts

A gas supply problem or a frozen condensate pipe are the most common causes of a Baxi E133 error but it could be caused by faulty boiler parts.

Here are some potential causes:

• Faulty gas valve: Might need a new one
• Worn-out spark electrode: Might need to be cleaned, bent or replaced
• Faulty PCB (printed circuit board): The PCB is the brain of the boiler and might need to be replaced

How to reset a Baxi boiler

The first thing I would do on a boiler that is not working, no matter what fault code is showing, is to check the pressure and reset the boiler. This is the simplest way to get your boiler working again, as it might have just locked out.

Modern Baxi boiler

To reset a modern Baxi boiler (eg 600 or 800), you must find the reset button. You must press the button to reset the boiler. Sometimes you have to hold it down for a few seconds, but on some Baxi boilers, it just needs to be pressed and released.

Older Baxi boiler

If it’s an older Baxi (Duo-tec, 105 etc..) with a knob to turn the boiler on and off, you will need to turn it fully anti-clockwise and hold it at ‘R’ for a few seconds until it resets.

Baxi E133 won’t reset

If your E133 error won’t reset, this means you have a problem that needs fixing before trying to reset it again. When the ignition has gone to lockout, it won’t reset until the cause of the error is fixed. If you have fixed a gas supply issue and it still won’t reset, this could mean there is air in the gas pipe. You should try resetting it a few times to get the gas into the boiler and get rid of the error code.

Baxi boiler guides

• Baxi boiler no hot water
• Baxi boiler low pressure
• Replace pressure relief valve
• Baxi boiler leaking
• Baxi E119 boiler fault

Conclusion

Fixing an E133 error is usually done by fixing a gas supply issue. On a cold winter night, an E133 fault is likely caused by a frozen condensate pipe. This is fixed by pouring hot water over the condensate pipe outside and resetting the boiler.

If you are sure you have gas and the condensate pipe isn't frozen or blocked, you should call a local gas engineer as it could need a part replacing.

Have any questions? Drop them in the comments below, I’ll do my best to help! If you found this post helpful, don’t forget to share it with others who might benefit.