Baxi 400 Fault Code: What It Means and How to Fix It
If your Baxi boiler is showing the 400 fault code, it usually means there’s a problem with water pressure or flow. This error can stop your boiler from working properly and leave you without heating or hot water. But don’t worry-many of the causes are simple to check and fix yourself.
Table of contents
What Does the Baxi 400 Fault Code Mean?
The Baxi 400 Error code means your boiler has detected low water pressure or poor water flow. This makes the boiler shut down to prevent damage. You’ll need to fix the issue before the boiler can start working again.
Common Reasons for the Baxi 400 Error Code
Here are some things that can cause the 400 Error Code:
- Water pressure is too low (usually below 1.0 bar)
- Air is trapped in the radiators or pipes
- The pump is blocked or not working
- A sensor or valve is broken
- There’s a leak in the system
How to Fix the Baxi 400 Fault Code
Follow the below given steps to fix baxi 400 fault code
- Check the Water Pressure
Look at the pressure gauge on the boiler-it should be between 1.0 and 1.5 bar. If it’s too low:
Find the filling loop (under the boiler)
Slowly open the valves to let water in
Close them when the pressure is back to normal - Bleed the Radiators
If you hear air or cold spots in your radiators, use a radiator key to let the air out until water flows. This helps the system work properly.
- Reset the Boiler
Once you’ve fixed the pressure or bled the system, press the reset button on the boiler. It should restart. Keep an eye on the pressure for a few days.
- Look for Leaks
Check around the boiler, radiators, and pipes for signs of leaking water. A leak will keep lowering the pressure until it’s fixed.
When to Call a Gas Safe Engineer
Some problems need expert help. You should call a Gas Safe registered engineer if:
- The fault code keeps coming back even after a reset
- You see water leaks inside the boiler
- The boiler is making unusual noises
- You think the pump or pressure sensor is broken
Never try to fix inside the boiler yourself it’s not safe unless you’re trained and qualified.
Preventing the Baxi 400 Error Code
You can avoid many boiler problems with simple care:
- Get a boiler service once a year
- Check water pressure regularly
- Bleed radiators before winter
- Fix leaks quickly
A well-maintained boiler is safer, lasts longer, and uses less energy.
Final Thoughts
The Baxi 400 fault code usually means low pressure or a blockage in the system. In many cases, you can fix it yourself with some basic checks. However, if the problem continues or you’re unsure what to do, it’s best to call a Gas Safe engineer. This way, you can avoid further damage or any potential safety risks.
Frequently Asked Questions
Fault code
System behaviour
3 Red flash
Ignition fault.Boiler has attempted to light 5 times and failed
4 Green flash
Communication error between printed circuit board (PCB) and control.Temporary error, will self reset.
2 Red flash
Boiler overheat tripped
The error E01. 04 indicates that Loss of flame was detected 5 times in 24 hours, There are many potential causes of a flame failing to light Condensate Pipe Blockage, Low Gas Pressure, Gas Valve Fault, or a fault in Ignition lead or Electrodes.
This Error code E04. 10 on your Baxi Boiler means that the Flow temperature sensor short-circuited. Sensor not or badly connected. It seems like the Sensor is faulty.
Most Baxi boilers have a simple reset button on the front panel – locate this and press and hold the button for 1 to 3 seconds or until it’s clear that the boiler has rebooted itself.
