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Boiler Advice

F28 Vaillant Fault Code Meaning and How To Fix It

F28 Vaillant Fault Code Meaning and How To Fix It

Vaillant F28 Fault code – What does the error mean & how to fix it?

Vaillant boilers are one of the most popular brands in the UK, so it is likely that at some point, people need to know what to do when they see an F28 error code.

  • The F28 error code, as defined by Vaillant, signifies an ignition fault, typically arising from factors such as insufficient gas supply, a malfunctioning electrode, or faulty ignition leads.
  • The F28 fault can be categorised either as an ignition issue or a problem with the gas valve.
  • Caution should be exercised when attempting to access the boiler casing or conducting repairs independently, as this can pose potential hazards.
  • It’s advisable to engage a qualified Gas Safe engineer to inspect and rectify any issues with your Vaillant boiler.

If you have previously undertaken repairs on your Vaillant boiler and encountered the F28 error, it might be prudent to consider investing in a new boiler. Older boilers tend to be less energy-efficient and may result in higher long-term costs.

Read our guide to new Vaillant boilers prices here for more information.

Vaillant boiler models F28 fault code is applicable to:

  • Vaillant Ecotec Pro
  • Vaillant Ecotec Plus,
  • Vaillant Turbomax

Get new boiler quotes online>

What does the Vaillant F28 fault code mean?

  • Failure during start-up: ignition unsuccessful

This means that the flame your water must pass over to heat it up before it reaches hot taps or circulates around the central heating system isn’t lit up.

This error code can have many causes. To diagnose the problem and fix it, a Gas Safe registered engineer will need to come to your home.

What causes the F28 error code?

  • Gas pressure regulator or gas meter defective
  • air in gas supply
  • Gas flow pressure too low
  • The thermal isolator device has been activated.
  • Frozen condensate pipe
  • Condensate duct blocked
  • Incorrect gas restrictor
  • incorrect ET gas valve fault
  • Faulty gas valve
  • Multiple plugs on PCB wrongly plugged in
  • Break in the cable harness
  • ignition system (ignition transformer, ignition cable, ignition plug, ignition electrode) defective,
  • ionisation current interrupted (cable, electrode),
  • Incorrect earthing of the boiler
  • electronics defective

How to fix a F28 Vaillant error code

When it comes to sorting out and fixing the F28 fault code on a Vaillant boiler, only a few of the fixes, such as the frozen condensate pipe, can be done by the average unqualified human being. All the others will require a registered Gas Safe engineer to get your hot water back up and running.

Gas supply fault

Verify that the gas meter is not accidentally turned off. Clients are often surprised at how many times the gas lever was accidentally left in the off or partially off positions. One way to check is to make sure your payment meter is up to date and that your gas supplier hasn’t cut you off, or other gas appliances are working.

Reset your boiler

To ensure that it is not a repeat occurrence, you may have to press the reset button 3 times. You should be alert for any future problems as these may indicate that there are deeper issues with your boiler and may need to be checked by a heating professional.

Frozen condensate pipe

Frozen condensate pipes are very common in the UK. Make sure that your condensate pipes are not blocked or frozen in extremely cold weather. If the weather is normal, condensate pipework may become blocked due to debris or blocked paths further down.

Faulty gas valve

Another problem is the gas-valves sticking because of internal lubrication/ seals hardening under cold weather. A gas engineer must perform this procedure as it involves removing the boiler case to reach the gas valve. This is a gas-carrying item and should only be performed by a gas heating engineer.

F27 is also known to have this fault code. F27 Vaillant fault code refers to failure immediately following ignition. Vaillant F28 error, however, is a complete failure.


The gas valve’s wiring connects to the printed circuit board (PCB) via the wiring. The valve won’t be able to communicate with the PCB if the wiring is damaged or loose.

Simply put, the PCB tells the gas valve when it should open or close. The valve will not function properly without these signals. It could even close when it is being told to, causing gas supply problems.

You won’t need a new gas tank if the wiring can be repaired. It is easy to fix wires.

Printed Circuit Board (PCB).

To determine exactly what the Vaillant boiler f28 fault code means, your boiler engineer can test every component and wiring. It’s worth inspecting the PCB to make sure the gas supply and gas valve are not the problems.

The PCB is interconnected with all internal components, ensuring that the boiler runs smoothly. The boiler will shut down if it fails to give the gas valve signals to open or close.

A Gas Safe engineer will inspect the PCB and check that the wiring connecting various boiler parts to it is in good condition. A replacement of a damaged or faulty PCB can cost several hundred pounds. It may be worth buying a new boiler.

Malfunctioning Electrodes

The electrodes in your boiler ignite the gas as it flows into the boiler. These electrodes, like all boiler parts, will wear down over time. They can wear down and make it impossible to ignite the boiler.

If the problem persists, a Gas Safe registered engineer will inspect them and recommend a replacement.

Preventing the F28 Error code on Vaillant boilers

the best way to prevent the F28 error code is to ensure you get a boiler service every year. Another option is to take out boiler cover, which prevents you from having to pay for any high Vaillant boiler repair costs.

If you think you’re boiler is knocking on a bit, don’t wait till you have a broken boiler with no hot water for days. You can get a brand new A-rated energy-efficient replacement boiler quote in under 20 seconds online now with one of our recommended installers.


What is the cause of the F28 fault on a Vaillant boiler?

The F28 fault code on a Vaillant boiler indicates an ignition or gas valve problem. Common causes include a mechanical fault with the gas valve, a frozen condensate pipe blockage, an electrical wiring fault, or low boiler pressure.

How do I fix the F28 error code on Vaillant boiler?

To fix the F28 error code on a Vaillant boiler, it is recommended to call a Gas Safe registered engineer. They can diagnose the problem and repair any ignition or gas valve problems. Do not attempt to repair the boiler yourself, as this could be dangerous.

How can I clear an F28 error code on my Vaillant boiler?

It is crucial to address the underlying issue causing the F28 error code before clearing it. A Gas Safe registered engineer should be called to diagnose and resolve the problem. Once the issue has been fixed, the engineer can reset the error code.

Is the F29 fault code related to F28 on Vaillant boilers?

Yes, the F29 fault code is related to the F28 error code on Vaillant boilers. Both codes indicate problems with the boiler’s ignition process. While F28 refers to a failure during start-up, F29 signifies flame loss during operation, which can also result from issues with the gas valve or wiring.

What is the difference between F28 and F54 fault codes on Vaillant boilers?

The F28 fault code indicates an ignition or gas valve issue, while the F54 fault code signifies a problem with the gas pressure sensor. Although both codes involve gas-related issues, the F54 code is specifically related to the sensor that monitors the boiler’s gas pressure.

How does cold weather influence the F28 error code on Vaillant boilers?

Cold weather can cause the condensate pipe to freeze and block, leading to the F28 error code. Insulating the pipe can help prevent freezing in cold conditions. If the pipe is frozen, gently thaw it with warm water or a hot water bottle and ensure it is insulated to avoid reoccurrence.

What steps can be taken to fix the F28 error on Vaillant Ecotec boilers?

To fix the F28 error on a Vaillant Ecofit Pure boiler, check if the gas supply is turned on and ensure the prepayment gas meter has enough credit. If the problem persists, it is recommended to call a Gas Safe registered engineer to diagnose and fix any issues related to ignition or gas valves. Always hire a professional to handle gas-related repairs for your safety.

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