Baxi Fault Codes: What They Mean and How to Fix Them
Estimated reading time: 12 minutes
Baxi boilers are trusted by homeowners for their performance and reliability. Whether you have a combi, system, or heat-only boiler, you may occasionally see Baxi fault codes appear on the boiler’s display. These codes are designed to help you quickly identify what’s gone wrong. They can range from ignition problems and sensor faults to low pressure or circulation issues.
This guide explains what Baxi fault codes mean, why they appear, and how to troubleshoot common issues before calling a Gas Safe registered engineer. Understanding these codes can save time, prevent panic, and help you restore heat and hot water faster.
Table of contents
- What Is a Fault Code on a Baxi Boiler?
- Types of Baxi Boiler Fault Codes
- Baxi Combi Boiler Fault Codes
- Baxi Fault Code E1 – Safety Lockout Triggered
- Baxi E118 – Low Water Pressure
- Baxi Error Code E133 – Ignition Failure or Gas Supply Issue
- Baxi Fault Code E160 – Fan Fault
- Baxi Fault Code E128 – Flame Loss During Operation
- Baxi Fault Code E50 – Hot Water Thermistor Fault
- Baxi Fault Code H.01 – Communication Error
- Baxi System Boiler Fault Codes
- Baxi Heat Only Boiler Fault Codes
- How to Reset Baxi Boiler
- When to Call a Gas Safe Engineer
- Conclusion
- Frequently Asked Questions
What Is a Fault Code on a Baxi Boiler?
A fault code is the boiler’s way of alerting you to a malfunction. Each Baxi boiler is fitted with sensors and internal checks that monitor performance and safety. When something isn’t right, the boiler displays a code, typically starting with an “E” (for error), followed by numbers. For example, E133 indicates ignition failure, while E118 means low pressure.
The code helps pinpoint the fault quickly and can guide homeowners or engineers in resolving the issue.
Types of Baxi Boiler Fault Codes
Fault codes vary by the type and model of boiler. Baxi boilers fall into three main categories: combi boilers, system boilers, and heat-only boilers. Each boiler type has common error messages, though some codes appear across multiple models.
Let’s explore the most common fault codes based on the type of Baxi boiler installed in your home.
Baxi Combi Boiler Fault Codes
Baxi combi boilers are compact, efficient, and popular in UK homes. These boilers heat water directly from the mains, removing the need for a hot water tank. Models include the Baxi 800 Combi, 600 Combi, 400 Combi, Duo-tec Compact, and Platinum Compact, including newer models like the Baxi 630, 830, 836, and 424 Combi 2.
While known for their reliability, these boilers may occasionally display fault codes.
Baxi Fault Code E1 – Safety Lockout Triggered
The E1 fault code signals that the boiler has shut down to protect itself. This can happen for several reasons, including low pressure, overheating, or a sensor fault. This fault usually points to over heating or sensor problems. If you want a more detailed breakdown, [read our full guide on the Baxi E1 fault code].
How to Troubleshoot
Check the pressure gauge and top up if needed. Turn the boiler off and back on again. If the E1 code persists, note any additional fault codes displayed and call a Gas Safe engineer for further diagnosis.
Baxi E118 – Low Water Pressure
This error appears when the system pressure drops below 0.5 bar, preventing the boiler from operating safely. This fault usually points to low water pressure problems. If you want a more detailed breakdown, [read our full guide on the Baxi E118 fault code].
How to Troubleshoot
Use the filling loop underneath the boiler to top up pressure to 1.0–1.5 bar. If pressure continues to drop, check for visible leaks or recently bled radiators. If you can’t find the cause, call an engineer.
Baxi Error Code E133 – Ignition Failure or Gas Supply Issue
This code appears when the boiler fails to ignite. Causes may include no gas supply, a frozen condensate pipe, or a faulty ignition system. This fault usually points to ignition failure or gas supply problems. If you want a more detailed breakdown, [read our full guide on the Baxi E133 fault code].
How to Troubleshoot
Make sure your gas supply is on. Test other gas appliances. In cold weather, check the condensate pipe for freezing. Try a reset. If the boiler still won’t ignite, contact a Gas Safe engineer.
Baxi Fault Code E160 – Fan Fault
This means the boiler’s fan isn’t working properly, preventing safe combustion. This fault usually points to fan problems. If you want a more detailed breakdown, [read our full guide on the Baxi E160 fault code].
How to Troubleshoot
You may hear strange noises or see the fan not starting. This requires professional inspection to repair or replace the fan or its wiring.
Baxi Fault Code E128 – Flame Loss During Operation
The boiler started successfully but lost the flame during use. This may indicate gas flow issues or an unsteady ignition. This fault usually points to flame loss during operation problems. If you want a more detailed breakdown, [read our full guide on the Baxi E128 fault code].
How to Troubleshoot
Ensure the gas is flowing properly. Try resetting the boiler. If the fault returns, an engineer may need to check the ignition probe or flame sensor.
Baxi Fault Code E50 – Hot Water Thermistor Fault
The thermistor checking outgoing water temperature is faulty, leading to inconsistent hot water. This fault usually points to hot water thermistor fault problems. If you want a more detailed breakdown, [read our full guide on the Baxi E50 fault code].
How to Troubleshoot
You’ll need an engineer to test and likely replace the faulty thermistor.
Baxi Fault Code H.01 – Communication Error
This typically refers to a communication loss between the gas valve and the control board. This fault usually points to communication error problems. If you want a more detailed breakdown, [read our full guide on the Baxi H.01 fault code].
How to Troubleshoot
Turn the boiler off and reset it. If the issue continues, it may need a replacement PCB or gas valve.
Baxi System Boiler Fault Codes
System boilers are ideal for homes with higher hot water demands and stored cylinders. Common models include the Baxi 600 System, 800 System, Platinum+ System, and Megaflo System.
These boilers offer excellent reliability but can display fault codes when internal sensors detect issues.
Baxi Fault Code E20 – Flow Thermistor Sensor Error
The boiler can’t accurately measure flow temperature, which may lead to performance issues. This fault usually points to flow thermistor sensor error problems. If you want a more detailed breakdown, [read our full guide on the Baxi E20 fault code].
How to Troubleshoot
Try a boiler reset. If the fault returns, the sensor may be damaged or disconnected and will need replacing.
Baxi Fault Code E40 – Return Thermistor Fault
This code appears when the return water temperature sensor malfunctions. This fault usually points to return thermistor fault problems. If you want a more detailed breakdown, [read our full guide on the Baxi E40 fault code].
How to Troubleshoot
Reset the boiler. If the issue comes back, an engineer should inspect and test the return thermistor.
Baxi Fault Code E78 – Water Pressure Sensor Error
This indicates the boiler can’t read pressure correctly, even if the gauge appears normal. This fault usually points to water pressure sensor error problems. If you want a more detailed breakdown, [read our full guide on the Baxi E78 fault code].
How to Troubleshoot
Try topping up pressure and resetting. If the code remains, the sensor likely needs replacement.
Baxi Fault Code E125 – Poor Water Circulation
The boiler detects poor water movement, often due to airlocks, low pressure, or a failing pump. This fault usually points to poor water circulation problems. If you want a more detailed breakdown, [read our full guide on the Baxi E125 fault code].
How to Troubleshoot
Check pressure and bleed radiators. If the system still struggles, the pump may need attention.
Baxi Fault Code E119 – Low Pressure
Like the E118 code, this points to insufficient pressure in the system. This fault usually points to low pressure problems. If you want a more detailed breakdown, [read our full guide on the Baxi E119 fault code].
How to Troubleshoot
Top up the boiler using the filling loop and monitor pressure regularly. If it drops repeatedly, inspect for leaks.
Baxi Fault Code E133 – No Ignition
This common code shows the boiler failed to light safely. This fault usually points to no ignition problems. If you want a more detailed breakdown, [read our full guide on the Baxi E133 fault code].
How to Troubleshoot
Ensure gas supply is available and reset the boiler. If no improvement, call a heating engineer.
Baxi Fault Code E160 – Fan Error
The fan may be stuck or disconnected. This fault usually points to fan error problems. If you want a more detailed breakdown, [read our full guide on the Baxi E160 fault code].
How to Troubleshoot
Reset the system. If the fan doesn’t operate, a professional should test or replace it.
Baxi Heat Only Boiler Fault Codes
Heat-only boilers are well-suited to larger properties and older heating systems that use a cold-water tank and hot water cylinder. Models include the Baxi Solo HE A, Baxi 200 Heat, Baxi 400 Heat, Baxi EcoBlue Heat, and Baxi 630 Heat.
These traditional boilers are dependable, but faults still occur from time to time.
Baxi Fault Code E28 – Flue Thermistor Fault
The boiler can’t detect flue temperature correctly, which may prevent safe operation. This fault usually points to flue thermistor fault problems. If you want a more detailed breakdown, [read our full guide on the Baxi E28 fault code].
How to Troubleshoot
Reset the boiler. If the fault returns, the thermistor likely needs replacing.
Baxi Fault Code E53 – Flue Obstruction
This code appears when the boiler senses blocked airflow through the flue. This fault usually points to flue obstruction problems. If you want a more detailed breakdown, [read our full guide on the Baxi E53 fault code].
How to Troubleshoot
Check the external flue for obstructions like leaves or snow. Do not dismantle the flue. Call an engineer for inspection.
Baxi Fault Code E55 – Calibration Required
The boiler needs recalibration after installation or part replacement. This fault usually points to calibration required problems. If you want a more detailed breakdown, [read our full guide on the Baxi E55 fault code].
How to Troubleshoot
This can only be done by a Gas Safe engineer using specialist tools.
Baxi Error Code E110 – Overheat Lockout
The boiler has exceeded safe temperature levels and has shut down. This fault usually points to overheat lockout problems. If you want a more detailed breakdown, [read our full guide on the Baxi E110 fault code].
How to Troubleshoot
Let the boiler cool. Check system pressure and bleed radiators. If overheating continues, professional inspection is required.
Baxi Fault Code E125 – Water Circulation Problem
Circulation is insufficient, often due to airlocks or pump failure. This fault usually points to water circulation problem problems. If you want a more detailed breakdown, [read our full guide on the Baxi E125 fault code].
How to Troubleshoot
Check pressure, bleed radiators, and reset. If no improvement, the pump may need replacement.
Baxi Error Code E133 – No Ignition Detected
The boiler failed to ignite. Causes include no gas, ignition issues, or condensate blockage. This fault usually points to no ignition detected problems.
How to Troubleshoot
Check gas supply and condensate pipe. If a reset fails, call a Gas Safe engineer.
How to Reset Baxi Boiler
Most Baxi boilers include a reset button on the control panel. On older models, press and hold the red reset button for 3 to 5 seconds. On newer models with a rotary control, turn the dial to the reset symbol, hold briefly, then return it to the desired setting.
Once reset, the boiler will attempt to restart. If the fault clears, it was likely a temporary glitch. If the code returns, further troubleshooting or an engineer visit may be needed. Check our step by step guide to reset Baxi boiler
When to Call a Gas Safe Engineer
While you can fix many Baxi error codes by checking water pressure, bleeding radiators, or pressing the reset button, some problems need expert attention. If the same error keeps coming back, your boiler has no heat or hot water despite normal pressure, or you hear unusual noises or notice leaks, it’s time to call a Gas Safe registered engineer. They can safely diagnose
deeper faults, replace damaged parts, and ensure your heating system works reliably and efficiently.
Conclusion
Baxi boiler fault codes offer quick insights into what’s wrong with your heating system. Most faults are minor and can be fixed by checking pressure, bleeding radiators, or resetting the boiler. If you’re unsure or the problem returns after a reset, always contact a Gas Safe registered engineer. If your boiler is under warranty, we recommend contacting Baxi customer support directly to ensure your coverage remains valid. For replacement parts or troubleshooting help, check our boiler spares section or contact our support team.
Frequently Asked Questions
On most Baxi boilers, the reset button is located on the front control panel. Some models have a dial that includes a reset setting. Turn the knob to “Reset,” hold it for a few seconds, then return it to your normal setting.
If the reset button doesn’t work, your boiler may still be locked due to an unresolved issue like low pressure, ignition failure, or sensor fault. Check the display for any error codes. If problems persist after a reset attempt, contact an engineer.
Cold radiators can be caused by trapped air, a faulty pump, low pressure, or a blocked system. Try bleeding your radiators first. If they still stay cold or heat unevenly, check your boiler pressure and system settings.
The serial number is usually found on a sticker on the inside of the boiler casing or behind the control panel. You may also find it in your installation manual or Gas Safe installation certificate.
Baxi offers warranties ranging from 2 to 10 years, depending on the model and if it was installed by a Baxi-approved installer. Check your warranty document or register your boiler on the Baxi website to confirm your coverage.
This may happen due to no gas supply, low water pressure, ignition failure, or a frozen condensate pipe. Check your display for fault codes and consult the user manual. If the issue isn’t easily fixed, call a Gas Safe engineer.
In freezing weather, the condensate pipe can freeze and block the boiler. To fix it, pour warm (not boiling) water over the pipe’s external section to thaw it. Then reset the boiler. If the issue continues, consider insulating the pipe.
Flashing lights on a Baxi boiler usually indicate a fault. A red flashing light often means ignition failure or a locked boiler. Use the fault code on the display to identify the problem. Refer to your manual or this guide to diagnose the issue.
A blinking red light usually means the boiler is in lockout mode. This could be due to flame failure, overheating, or low pressure. Identify the fault code and try resetting the boiler. If the light persists, seek expert help.
