Glow-worm F29

Glow-worm F29 Fault Code Guide: Common Causes and Fixes

Last updated on June 10th, 2024

The Glow-worm F29 fault code will show on the boilers screen when there is a problem and it locks out.

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

Having fault codes on the screen is a great way to help diagnose your boiler problems.

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.

Glow-worm combi boiler

What Does F29 Mean on a Glow-worm Boiler?

Here is what the Glow-worm manual says about the F.29 fault code:

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

The most likely cause of an F29 fault code on a Glow-worm boiler 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 Glow-worm Boiler

To fix the Glow-worm 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 Glow-worm F29 Fault

A gas supply problem is the most common cause of a Glow-worm 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. 

Gas Pressure

Low gas pressure (or no gas) is a common cause of an Glow-worm F29 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.

Glow-worm F29 Fault Reset

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

Glow worm heating dial

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

To reset a Glow-worm 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 Glow-worm boilers, it just needs to be pressed.

Glow-worm Boiler Guides


A Glow-worm 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.

F29 Glow-worm Fault Code FAQs

What is the life expectancy of a Glow-worm boiler?

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

I have replaced Glow-worm boilers less than 10 years old and they could last 20-30 years but Glow-worm say 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 Glow-worm boiler?

An F28 Glow-worm 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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