Vaillant F29 Fault Code: What Does it Mean & How to Fix it?

Oscar Garner

By Oscar Garner

Last Updated on June, 2024

Having your central heating system break down during the colder months can be extremely bothersome, especially when you are right in the middle of relaxing in bed and watching your comfort TV show. 

You check your Vaillant boiler to see what the issue is and notice the F29 error code on it. But what does it mean? 

Don’t worry; we’re here to help! In this article, we’ll be breaking down what the Vaillant F29 error code is, the potential causes of the F29 error code and possible solutions to these issues, how to avoid the Vaillant F29 fault code from occurring, and so much more to know about your Vaillant boiler!

So, don’t give up just yet! With a few steps and following the manufacturer’s instructions, you can get your central heating system up and running in no time. 

What Does Vaillant F29 Fault Code Mean? 

Simply put, the F29 error code indicates that your boiler’s flame isn’t working during its operation, leading to your boiler shutting down automatically (also known as a ‘boiler lockout’).

Although this can be inconvenient, a boiler lockout is a safety measure that prevents potential gas buildup in your home. The flame is crucial for generating heat and hot water. Without the boiler flame, your boiler becomes essentially non-functional. 

In layman’s terms, it means that until the F29 error is resolved, you won’t have access to heating or warm water. 

What Causes the Vaillant F29 Error Code and How to Fix Them?

a picture of a Vaillant ecotec boiler with the fault code of f29

There are many reasons why Vaillant boilers show the F29 error (in other words, why your boiler flame has stopped working).

Some of them can be solved on your own, while others may require the assistance of a Gas Safe registered engineer. Here are the common causes of flame failure in Vaillant Ecotec Boilers: 

Insufficient Gas Supply

A common reason for the F29 fault is an issue with your gas supply. If your Vaillant boiler isn’t receiving enough gas due to low pressure, it won’t function properly and will show the F29 fault. 

Solving this is easy– just check if your gas metre is turned on and ensure there’s enough credit if you have a prepaid gas metre. 

It’s also wise to regularly monitor your gas supply to ensure it remains stable. Fluctuations in gas pressure can trigger the error. By staying aware of your gas supply, you can prevent these issues and keep your boiler running smoothly. 

Faulty Gas Valve 

Faulty gas valves are another reason for the F29 fault. If your gas valve is defective, it can impede the gas flow, causing your Vaillant boiler to malfunction. 

If you suspect this is the issue behind the error, seeking professional help from a Gas Safe registered engineer is crucial. Fixing a faulty gas valve isn’t a task you can do on your own. It requires assessment and intervention by a professional Gas Safe engineer. 

These heating engineers possess the expertise to safely and efficiently repair or replace the faulty gas valve, ensuring your boiler is functioning properly. 

Low Gas Pressure

An F29 fault code can occur if your gas pressure is too low. The correct gas pressure is crucial for maintaining the boiler’s flame and overall operations. 

Low gas pressure can stem from incorrectly adjusted or faulty gas valves. However, blockages or leaks could also be contributing factors. 

Frozen Condensate Pipe 

a picture of a Frozen Condensate Pipe in a water boiler

The error can occur if the condensate pipe, which removes waste liquid from your boiler, becomes frozen or blocked. If this is the case, you will be able to hear unusual sounds like gurgling from your boiler. 

Other less frequent causes could include strong winds, freezing of the gas metre regulator, or blockages in the pipework. If you suspect a frozen condensate pipe, you may be able to resolve this issue yourself with the right skills and knowledge. 

First, locate the condensate pipe and identify where the blockage or ice is occurring. It usually happens around the joints. Next, pour warm water over the affected area– this should help clear the blockage without hindering your safety. 

Ensure you turn off the gas supply before pouring warm water over the condensate pipe. Since your boiler isn’t operational anyway, this precaution won’t disrupt your heating, but remember to turn it back on once the issue is fixed. 

If you’re uncertain about handling a frozen condensate pipe, hiring a Gas Safe registered engineer is best for diagnosing and resolving the issue. 

The Flue is Not Working

When your boiler is not in use, the flue is responsible for safely venting harmful gases outside. The flue is typically identified by ducts on your roof or the sides of your house. Faults in the flue can be caused by blockages or poor installation. 

A poorly installed boiler flue can be blown out by strong wind, potentially causing flame failure and an ignition error. 

The F29 fault could indicate issues with the flue. It’s crucial to have faulty flues repaired by a Gas Safe engineer. They will ensure the flue is installed correctly and repair or replace it if needed. 

To ensure safe gas flow through your home, Gas Safe engineers can clear any obstructions in the flue pipe and install a flue guard if needed to prevent future blockages. 


Accumulated debris inside the boiler burner can prevent proper ignition. Now, you won’t be throwing trash inside your boiler on purpose, but general use can lead to debris buildup over time. 

If your boiler hasn’t been serviced for many years, there’s a higher chance that debris accumulation is causing the F29 fault. 

Regular boiler servicing includes cleaning the boiler burner, so neglecting boiler maintenance for an extended period could allow debris to gather and cause issues. 

Cleaning the debris off the burner usually resolves the problem. However, if damage has occurred, a boiler replacement may be necessary. 

Lead Problems or Ignition Electrode

The ignition electrode generates the spark that lights the flame in your boiler. If the electrode becomes dirty due to having no regular maintenance, it can malfunction and prevent your boiler from igniting, resulting in the F29 fault. 

Besides dirt and debris, factors like old age and internal water leaks can also cause the electrode to fail. To fix this issue, contact a Gas Safe engineer to diagnose the problem and repair or replace the faulty component.

Hiring a Heating Engineer to Fix an F29 Fault 

If your boiler is showing the F29 error for reasons like condensate pipes or debris blockage, you may be able to fix the problem on your own. However, in more serious cases, you will require a boiler engineer to look at your boiler. 

A Gas Safe Registered engineer typically charges between £30 and £60 per hour for their services. The duration of the work can vary, ranging from less than an hour to several hours, depending on the problem and its complexity. 

How to Prevent the F29 Fault? 

Prevention is key when it comes to boiler issues, as it’s more cost-effective than dealing with repairs later on. Here are some steps you can take to keep your boiler operating smoothly and your home warm: 

Schedule Regular Maintenance

Arrange for your boiler to be serviced annually by a qualified engineer. This maintenance helps catch and address any potential issues early on, preventing more significant problems down the road. 

It also ensures that your boiler operates efficiently, saving you money on energy bills and repairs. 

Check the Flue Regularly

The flue is critical in removing harmful gases from your boiler’s combustion process. Regularly inspect the flue to ensure it’s clear of debris and blockages. 

A blocked flue can lead to carbon monoxide poisoning, which is extremely dangerous. Consider having a Gas Safe Engineer check the flue during your annual maintenance visit. 

Don’t Ignore Warning Signs

If you notice unusual sounds or odours, or if your boiler isn’t working correctly, don’t ignore these signs. They could indicate more serious underlying issues that may lead to breakdown or safety hazards. Contact a qualified engineer quickly to diagnose and fix any issues. 

Other Common Fault Codes

a person fixing a vaillant water boiler

The F29 fault code isn’t the only error your boiler can experience. Below is a list of fault codes that can help you control any issues with your boiler. 

  • F.00: Heating Flow Temperature Sensor Interruption.
  • F.01: Failure To Ignite.
  • F.02: An Issue With The Flame During Normal Operations.
  • F.03: A Fault In The Fan. 
  • F.10: Flow NTC Short Circuit. 
  • F.11: A Short Circuit On The Heating Return NTC Thermistor. 
  • F.12: Issue With Your Heating Flow Thermister (NTC) And Sensor Plug. 
  • F.13: Issue With Your Heating Flow Thermister (NTC). 
  • F.20: Overheating. 
  • F.22: The Water Pressure Has Fallen Low. 
  • F.23: Safety Shut Down Due To Excessive Temperature Variation. 
  • F.24: Not Enough Water In The Boiler. 
  • F.25: The Flow Temperature Has Gone Up Too Quickly. 
  • F.26: The Gas Valve Activated Via The Gas Stepper Motor Has Stopped Working. 
  • F.27: An Incorrect Flame Has Been Detected. 
  • F.28: Ignition Or Gas Valve Problems. (Read more about it here.)
  • F.29: Flame Failure. 
  • F.32: Fault In The Air System. 
  • F.49: An Issue With The eBus Connection. 
  • F.52: Connection Fault With The Mass Flow Sensor. 
  • F.53: Flow Sensor Function Is Faulty. 
  • F.54: Not Receiving The Gas Quantities Needed To Ignite The Flame. 
  • F.56: Gas Valve Defective. 
  • F.57: The Ignition Electrode Is Corroded. 
  • F.61:  A Fault With Either Your Gas Valve, The Wiring Harness, Or The PCB. 
  • F.62: The Gas Valve Hasn’t Closed When The Boiler Is Turned Off. 
  • F.63: Problem With The PCB.
  • F.64: The Flow And Return Sensors Are Defective. 
  • F.65: Overheated Electronics. 
  • F.67: Electronic Fault In The Flame System. 
  • F.68: Unstable Flame Signal. 
  • F.70: The PCB Has Not Been Assigned Its Software Identity For The Model Of Boiler It Is Intended For. 
  • F.71: Disconnected Or Defective Heating Flow NTC Thermistor. 
  • F.72: The Communication Between The PCB/Thermistors Is Damaged Or Faulty Wiring.
  • F.73: No Communication Between The Pressure Sensor And The PCB. 
  • F.74: The PCB Is Detecting A Short Circuit Or Excessively High Voltage Back From The Pressure Sensor. 
  • F.75: Your Boiler Can’t Register A Pressure Change When The Pump Turns On. 
  • F.76: Too Much Heat Stress Being Applied To The Primary Heat Exchanger. 
  • F.77: No Response From The Flue. 
  • F.78: Interruption To DHW Outlet Sensor At External Controller, Link Box Is Connected, But Hot Water NTC Is Not Bridged. 
  • F.80: actoSTOR Inlet Sensor Fault. 
  • F.81: Lack Of Hot Water. 
  • F.83: The Boiler Detected A Temperature Difference In The Return Or Flow Pipes.
  • F.84: The Boiler Detected A Permanent Temperature Difference Between Flow And Return Pipes.
  • F.85: Error With Flow And Return Temperature, Sensor Incorrectly Fitted. 
  • F.90: Communication With actoSTOR Module Has Been Interrupted. 
  • F.91: Lack Of Hot Water. 
  • F.92: The Coding Resistor On The PCB Does Not Match The Gas Group That Is Entered. 
  • F.93: Gas Group Fault. 



Having your heating system down during low temperatures can be frustrating. Be it a flue issue or an issue with your gas supply, we have covered why your Vaillant boiler is showing the F29 error code. 

If the problem is more complicated than you thought, be sure to contact a Gas Safe engineer to handle any technical issues. 

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