F29 Vaillant boiler fault

F29 Vaillant Fault Code Help Guide: Causes and Fixes

Last updated on June 10th, 2024

The Vaillant boiler F29 fault code, and all Vaillant boiler fault codes, show on the display when there is a problem and your boiler locks out.

Vaillant uses them to show you what might be wrong with the boiler not firing up.

I have been a full-time boiler repairer for over a decade and having fault codes on the screen when I arrive is very welcome.

In this post, I’ll go through some of the reasons for your F29 fault and some potential fixes.

What Does F29 Mean on a Vaillant Boiler?

Here is what the Vaillant Ecotec manual says about their F.29 fault code:

What Does F29 Mean on a Vaillant Boiler
Vaillant F.29 fault meaning

The most likely cause of an F29 fault code on a Vaillant boiler (the same as Glow-worm F29) is the boiler has been locked out due to a gas supply fault or a blocked condensate pipe.

An F29 fault code could also mean that a part on the boiler is broken and needs to be replaced, but most of the time it is a gas supply issue.

How to Fix F29 Fault on a Vaillant Boiler

To fix the Vaillant F29 fault code on your boiler, the first thing I would do is check:

  • The gas is turned on at the gas meter
  • If you have a prepayment gas meter, then make sure you are in credit, as this is quite a common situation I come across
  • If you have other gas appliances, like a gas hob or gas fire, then check to see if these are working to find out if you have a gas problem. If they don’t work, then you have a gas supply problem
  • Check for a blocked or frozen condensate pipe
Gas meter ecv turned off
Gas meter ECV turned off

Other Causes of F29 Vaillant Fault

A gas supply problem is the most common cause of a Vaillant F29 fault code, but here are some other potential causes:

  • Faulty gas valve: Might need a new one
  • Worn-out spark electrodes: Might need to be cleaned or replaced
  • Faulty PCB (printed circuit board): The PCB is the brain of the boiler and might need to be replaced
  • Frozen condensate pipe: If it’s freezing outside, then having a frozen condensate pipe is possible. You can pour hot water on it to melt the frozen condensate and reset the boiler. Dealing with frozen condensate pipes on Vaillant boilers

Gas Pressure

Low gas pressure (or no gas) is a common cause of an F29 Vaillant fault code. You need to make sure you’re getting enough gas but low gas pressure can also be caused by a faulty gas valve.

You can do all the checks needed to find out if you’re getting enough gas but you might need to get a Gas Safe engineer in to replace a faulty gas valve.

You also might need to call your gas supplier if your other gas appliances aren’t working as there might be a problem with your gas meter or a gas pipe problem in the street.

Vaillant F29 Fault Reset

The first thing I would do on a Vaillant boiler that is not working, no matter what fault code is showing, is to check the pressure and reset the boiler.

Vaillant boiler reset button
Vaillant reset button

Knowing how to reset a Vaillant boiler is the simplest way to get your boiler working again, as it might have just locked out.

To reset a Vaillant boiler, you must find the reset button. This is usually a flame with a line through it.

You have to press the button to reset the boiler. Sometimes you have to hold it down for 3 seconds, but on some Vaillant boilers, it just needs to be pressed.

Vaillant Boiler Guides


A Vaillant F29 error on your boiler can be easily fixed without opening the boiler.

Make sure to verify you are getting gas by checking the gas meter ECV and that you have credit if you use a pre-payment gas meter.

If it’s freezing outside then you probably have a frozen condensate pipe.

If it’s not any of these problems then it’s probably a gas valve or PCB problem which you’ll need to call a Gas Safe engineer to fix.

Feel free to ask me any questions in the comment section below and I’ll try my best to help.

Please share this post if you find it helpful.


What is the life expectancy of a Vaillant boiler?

The life expectancy of a Vaillant combi boiler is around 15 years. This varies greatly depending on things including how well looked after the boiler is with servicing and how often it’s used.

I have replaced Vaillant boilers less than 10 years old and they could last 20-30 years but Vaillant says around 15 years for the life expectancy.

How do I clear F29 error code?

To clear the F29 error you can try resetting the boiler. This will try to restart the boiler and if it was just a glitch causing the error code then your boiler should work. But, most likely you will have to find and fix the problem before the error code will clear and this might mean that you’ll need a Gas Safe registered engineer.

What causes F28 fault on a Vaillant boiler?

An F28 Vaillant fault is similar to an F29 error is an ignition fault and can be caused by insufficient gas or other F29 problems in this post. You should check the gas supply and condensate pipe first.


  • Steven Reid

    I am a full-time plumber and Gas Safe registered engineer. I incorporated Housewarm Ltd. in 2011 to provide heating and plumbing services to homes in Newcastle upon Tyne, England. I now blog about what I've learned over the years to help DIYers and plumbers.

    View all posts
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