Vaillant f27 fault code

Vaillant F27 is a common error code in ecoTEC PRO and PLUS boilers. It’s most commonly found between 2005 and 2012 models and will likely require a boiler repair.

Most often, it is caused by moisture that affects the electrical components or a defective PCB of a Vaillant boiler. This can occur along with the F61 or F62, both of which relate to gas valves that are defective.

This problem requires you to examine ignition components and the gas supply in your Vaillant boiler. You must contact a Gas Safe registered engineer in order to fix this error.

What does the Vaillant F27 Error mean?

F27 is an error code that indicates that the Vaillant boiler detected an ‘incorrect flame’. This simply means that the boiler detected that the gas and flame ratio is not balanced enough to allow the boiler’s operation.

A Vaillant F27 error causes a lock out. This means that your hot water and central heating won’t function until the error is corrected.

What Causes an F27 Vaillant Error?

On Vaillant boilers the manufacturer claims that an F27 error code can be attributed to a defective flame sensor. However, there could be other causes.

A broken spark electrode or ignition leads

The spark electrodes or ignition leads could be too worn to cause this error code. These parts produce the flame. If they become worn or damaged, the flame will not ignite correctly and trigger the F27 code.

If the Vaillant ecoTEC boiler isn’t firing, this is likely to be the problem.

Moisture on electrical components

Moisture on the electrical components is the most common reason for an F27 fault.

It could be water getting on the parts, or it could be water dripping onto them and you will need a gas engineer to fix this problem. If you’re boiler loses pressure quickly or often then this may be the issue

Malfunctioning PCB

The F27 can be triggered by an electric malfunction but it is not always moisture-related. F27 is also triggered by a PCB failure.

The PCB controls all electrical components of the boiler including the flame sensor and temperature sensors. It can also cause problems when it malfunctions.

If you are seeing this:

  • A flashing display panel
  • Poor temperature regulation
  • Pump or fan failure

If this is the reason your F27 code has shown, the flame in the boiler will not be affected – the fault PCB caused an error code to display.

This doesn’t mean that nothing should be done. The PCB is the brain and it needs to be fixed if it fails or is damaged.

Gas valve not working correctly

The gas valve allows gas to enter the boiler. It also controls how much gas is allowed in. It must supply the boiler with enough gas to ensure the flame is produced. If your vaillant boiler is showing the F27 fault code for this reason you will definitely need to call a gas engineer.

Defective flame sensor

It can be the reason, according to the manufacturer’s instructions. However, it isn’t common. An engineer can easily test it – if the device conducts electricity and is clean, it will work fine.

How to Fix an F27 Vaillant Error

You will need to contact a gas safe engineer in order to correct this error.

If the problem is not the PCB, the fastest and most cost-effective option will be to replace the defective parts. These parts are costly and take a lot of time to replace. You should replace the boiler if it is more than 8 years old.

How can you fix a Vaillant F27 error yourself?

If you suspect that there is a leak in your system, and you think it might be contributing to the Vaillant F27 error code then turn off your water supply until an expert can fix it.

An indicator of a leak is a sudden drop in water pressure in your Vaillant boiler.

This error cannot be corrected by you. You are using a gas appliance when you open the boiler cover. If you don’t have a Gas Safe certificate, it isn’t safe.

It’s easy to miss the F27 problem and replace the wrong parts. This can lead to huge, unnecessary expenses.

Contact a Gas Safe Engineer to resolve this issue.


My Vaillant boiler is losing pressure.

Low pressure by itself will not cause a Vaillant F27 code. If your boiler leaks say from your heat exchanger, low pressure could lead to water entering the electrical components. This could trigger an F27.

Can I reset my boiler to fix an F27 error

Resetting the boiler will not only clear the fault code, but it will also fix the problem.

After the boiler displays an error code, you can reset it. However, if the boiler is not fixed immediately, the boiler will display the error code again.

After the gas safe registered engineer has fixed the problem, restart your boiler.

Can ignition leads and electrodes be reconditioned rather than replaced?

Yes, they can be replaced if that is the cause of the problem. However, this should not exceed £120 and be completed by gas engineers if you need a gas Vaillant boiler repair.

The boiler will not turn off if it displays an F27 error code.

The code will show you the code the first time it is displayed.

It will eventually lockout and stop being reset. It is best to call a Gas Safe Engineer immediately you see this Vaillant boiler fault code

Does the F27 fault code mean I need a new boiler?

All the top Gas Safe engineers are available to help you and you can get a fixed price quote online for a full boiler installation. If you have an old boiler that is over 10 years old, then a new boiler may be a better option. Vaillant boilers become less energy efficient over time too so you could start saving on your gas bills right away.

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