Vaillant boiler F28 fault code

How to Fix Vaillant Boiler F28 Fault Code

The Vaillant Boiler F28 fault code, and all Vaillant boiler fault codes, show on the screen on the front of the boiler when there is a problem and your boiler locks out.

Vaillant uses them to show you what might be wrong with the boiler. Having fault codes on the screen is a great way to help diagnose your boiler problems.

I have been carrying out boiler repairs for over 10 years and having fault codes on the screen when I arrive is very welcome. Not all boilers use fault codes, so having them is a huge bonus.

What Does F28 Mean on a Vaillant Boiler?

The most likely cause of an F28 fault code on a Vaillant boiler is the boiler has been locked out due to not getting any gas. This can be checked quite easily without having to open up the boiler. This is similar to the Vaillant boiler F54 fault code.

An F28 fault code could also mean that a part on the boiler is broken and needs to be replaced, but most of the time in my experience it is a gas supply issue.

How to Fix F28 Fault on a Vaillant Boiler

To fix the F28 fault code on your Vaillant boiler, the first thing I would check is that 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 supply problem. If they don’t work, then you might have to contact your gas supplier.

Other Causes of an F28 Fault Code

A gas supply problem is the most common cause of a Vaillant boiler f28 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 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.

How to Reset a Vaillant Boiler

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.

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.

How to reset a Vaillant boiler
Vaillant boiler reset button.

Vaillant Boiler F28 Fault Code FAQs (Frequently Asked Questions)


How do You Clear the Fault Code on a Vaillant Boiler?

To clear the fault code on a Vaillant boiler, you must reset the boiler. If the fault code appears after resetting the boiler, you will need to find and repair the problem causing your Vaillant boiler to lock out and show a fault code.

Why is My Vaillant Boiler Not Turning On?

If your Vaillant boiler is not turning on at all, nothing on the display, then you probably have an electric supply issue.

You should check the fused spur switch that should be next to the boiler. Make sure it is switched on and the 3 amp fuse is good. It could also be that the fuse at the main board (consumer unit) has tripped, so you can there also.

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