Vaillant boiler fault codes

Vaillant Boiler Fault Codes in Simple Terms (2022)

Vaillant boiler fault codes are codes used by Vaillant to show you the problem with your boiler when it has broken down or is not working correctly, which should help you learn what the problem is and how to fix it.

Not all boiler manufacturers use fault codes, but it does help boiler repairers when attending boiler break-downs as it gives us a place to start and sometimes the problem is diagnosed instantly because of Vaillant’s boiler fault codes.

I have been repairing boilers for over 10 years and the quicker you fix it the better, so having the boiler’s fault code on the screen when you show up is sometimes a great start.

Here I’ll show you the most common fault codes and the most common cause which can show you how to fix Vaillant boiler problems.

Common Vaillant Boiler Fault Codes and Causes

Here are some of the most common Vaillant boiler fault codes, with links to posts that go into more detail.

  • Vaillant Boiler F22 Fault Code – Low water pressure – Commonly caused by a leak or from someone bleeding air out of radiators. You might just need to repressurise the boiler.
  • Vaillant Boiler F75 Fault Code – Pressure sensor – Commonly caused by dirty water in your central heating system. You might need to clean or replace the pressure sensor.
  • Vaillant Boiler F28 Fault Code – No gas – Check if the gas is turned on at the gas meter and make sure there is credit on if it is a prepayment meter.
  • Vaillant Boiler F29 Fault Code – No flame detected
  • Vaillant Boiler F27 Fault Code – Incorrect flame detection
  • Vaillant Boiler F83 Fault Code – Temperature sensor
  • Vaillant Boiler F54 Fault Code – Insufficient gas supply
  • Vaillant Boiler F25 Fault Code – Temperature rising too quickly on the flow
  • Vaillant Boiler F73 Fault Code – No pressure change when the pump starts

How to Reset a Vaillant Boiler

The first thing I would check 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 Pressure Gauge

Vaillant boilers have annoying manual pressure gauges which don’t have any numbers on them, so most people don’t know if it’s on the correct pressure. It always looks like the pressure is low, even though it’s not. This can lead to raising the pressure too much.

You have to read the digital pressure gauge on the screen to know for sure, but you have to press multiple buttons to find it. Which can also be annoying when working on Vaillant boilers.

Vaillant Boiler Problems

Vaillant boilers, like other boilers, have problems. No heating, no hot water, the boiler is leaking, there are lots of problems Vaillant boilers have. Some you can learn how to fix yourself, but some will need a registered gas engineer to fix it.

Vaillant Boiler Fault Codes FAQs (Frequently Asked Questions)


How do you clear the fault code on a Vaillant boiler?

You clear the fault code on a Vaillant boiler by resetting the boiler. You do this by pressing, and sometimes holding, the reset button.

If the fault code does not clear after resetting, then you will need to fix the problem that is causing the fault code and the boiler to lock out.

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