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Vaillant F28 Error: What it is (and how to fix it)

F28, no, it's not a fighter jet. It's an error code which pops up surprisingly often on many Vaillant boilers. Have you been a victim of the F28 code? Help is at hand, at Heatable.

Are you receiving the F28 fault on the Vaillant boiler's control panel and want to know what it means? 

In this post, we will explain what the F28 error code can mean and what you can do to resolve the issue and get your boiler back in working order in next to no time.  

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Resolving the Vaillant boiler F28 error 

If your boiler is displaying an error code, you might be tempted to simply restart your boiler and ignore the code.

Vaillant F28

However, this is unlikely to resolve the issue and ultimately your boiler stops operating for three important reasons: 

  • To protect the boiler from damage 
  • To keep everyone on the property safe
  • To annoy you on a very cold day

It is also important to never tamper with the boiler yourself, or open the casing, as this can be dangerous. Instead, the best thing you can do is to get your boiler investigated and fixed by a qualified Gas Safe Engineer. 

What causes the Vaillant boiler F28 error? 

The Vaillant boiler F28 error code is displayed on the following Vaillant boiler models: 

  • Vaillant ecoTEC Pro
  • ecoTEC Pro Plus
  • Turbomax Plus 824/828E

The F28 code is displayed when your boiler fails three ignition attempts, resulting in the boiler halting operation and turning off. 

F28 Error Code

Vaillant officially defines the F28 error code as an ignition fault. There are many potential causes to this problem including an insufficient supply of gas, a faulty electrode or ignition lead. 

Therefore, the causes of the F28 fault can be broadly categorised into either an ignition fault or a gas valve fault.

Vaillant ecoTEC F28

This issue results in a boiler failure since the ignition is required to light the gas and create the flame that the cold water passes over to become heated. Since it is faulty, the hot water can no longer become heated, meaning no hot water can be supplied to your taps or your central heating system. 

Think you may have an on-going issue with your boiler? Check our list of the top 10 boiler problems common in all types of boilers

Vaillant F28 fault code fixes 

When diagnosing the cause of the f28 fault code on your boiler, a registered Gas Safe Engineer will likely inspect the following boiler components: 

Gas supply issue 

F28 Gas Supply Issues

One of the most common causes of an f28 error code being displayed is a gas supply fault.

i.e. no gas supply to your boiler

You can easily test if this is the likely cause yourself by attempting to turn on other gas appliances in your home and seeing if they work or not.

i.e. a cooker, or fire

If there is no gas supply, this may be caused by your energy company cutting off supply, gas infrastructure work currently taking place in your area, or, you may have simply not topped up your meter (if you have one).  

Looking to pay for your new boiler monthly? Refer to our boilers on finance guide for more info.

Learn all about combi boilers in our what is a combi boiler guide. 

Faulty gas valve 

Faulty Gas Valve F28

A gas valve fault is another common cause of an f28 error.

The gas valves main role is to control the supply of gas into the boiler, so when there is an issue no fuel can be ignited to heat the water. 

A fault with the gas valve can be a result of either a wiring or mechanical fault.

Cost to fix: £150-300

Wiring fault 

F28 Wiring Fault

For example, boiler components are connected electronically to the printed circuit board (PCB), which is the control centre of the boiler, responsible for controlling and coordinating the various boiler components. 

Therefore, if a wire is loose or disconnected between the gas valve and PCB, the signals will no longer be transmitted, resulting in the gas valve malfunctioning, causing the boiler to shut off.

Cost to fix: £100-500

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Mechanical fault 

Alternatively, the gas valve may not be working due to a mechanical fault. With time, the valve is susceptible to wear and tear, resulting in the valve sticking. 


Want an exact price on a new boiler? Use our boiler quote calculator (your fixed price will appear on screen).

A gas valve that is prone to sticking will no longer be able to reliably carry out its function – to open and close whenever gas is required. As a result, this can cause the boiler to shut off and display the f28 error code. 

Cost to fix: £100-300

Faulty electrodes 

F28 faulty electrodes

When the gas enters the boiler via the valve, it needs to be ignited by the electrodes, however, if they are faulty, they will no longer be able to ignite the gas and create the flame. 

Over time, the electrodes can become worn and may need to be cleaned or replaced, in which case a registered Gas Safe Engineer can do this.  

Cost to fix: £100-300

Frozen condensate pipe 

Frozen Condensate F28

The condensate pipes job is to direct toxic flue exhaust fumes/vapour/residue to the outside of your property, so when this becomes blocked it can be a safety hazard, hence why the boiler will shut off until the issue is resolved. 

Traditionally, condensate pipes tend to freeze in winter, resulting in a blocked pipe. To resolve this, a Gas Safe Engineer can defrost the pipe to get the contents flowing again. 

Thankfully, modern boilers such as Worcester Bosches Greenstar Range are equipped with CondenseSure, this is a feature designed to prevent condensate pipes from freezing. 

Cost to fix: £50-100

PCB fault 

PCB Fault

The printed circuit board is the processing unit of the boiler and is wired up and receives signals from many of the boiler’s components, controlling their function and ensuring they coordinate together as intended. 

However, if a wire is loose or disconnected from a component and the PCB, or the PCB is faulty, it could result in the boiler shutting off and displaying the f28 error code. 

Cost to fix: £100-500

Check our new boiler costs guide and use our boiler size calculator if you want to get a better understanding of how our fixed price boiler quote tool works. 

Fixing the Vaillant F28 Error Code 

The best way to resolve the F28 error code is to seek the help of a registered Gas Safe Engineer, who will be able to diagnose and repair whatever is causing the f28 code to be displayed.

Use this clickable form to get a fixed price on the screen instantly.

If your boiler is old, in-efficient and letting you down - what's the point in fixing it? 

At Heatable, we can install you with a boiler replacement, with a 10 year parts and labour warranty, from as little as £1,695, within 24 hours. Get your fixed price online in 90 seconds.

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