Vaillant boilers fault codes
Vaillant boilers report faults as an F code on the display, and the numbering has stayed broadly consistent across the ecoTEC range since 2005. That is useful: an F.22 on a 2008 ecoTEC plus means the same thing as an F.22 on a 2023 ecoTEC exclusive. What changes between generations is the reset procedure and, on the newer units, how much extra detail the display gives you alongside the number.
Where the code shows on a Vaillant
On ecoTEC models the code appears on the main display as F followed by a full stop and a number — F.22, F.75. Older units show it only while the fault is live; newer ones keep it in the fault memory, which you reach by holding the two centre buttons together.
How to reset a Vaillant
Hold the reset button (the one marked with a flame and a cross, or on newer units the button under the display) for about three seconds until the display clears. Never reset more than twice for the same fault — a code that comes straight back is telling you something real.
Most common Vaillant faults
The Vaillant codes people look up most.
- F.22Get it checkedThe boiler has shut down because there is not enough water in the system. Pressure has dropped below roughly 0.5 bar and it will not fire until you top it up.
- F.75Get it checkedThe boiler cannot detect a rise in pressure when the pump starts, so it has locked out. Usually a failed pressure sensor or a pump that is not moving water.
- F.28Stop — call an engineerThe boiler tried to light and failed three times in a row, so it has shut the gas off and locked out. Do not keep resetting it.
- F.29Stop — call an engineerThe boiler lit correctly and then lost the flame while it was running. It has shut the gas off and locked out, and it needs an engineer.
Every Vaillant fault code
14 published codes. Filtering happens in the page — every code is in the HTML.
Showing 14 of 14 codes
Vaillant models
Codes can differ between generations. Check yours.
Guides that help with Vaillant faults
How to repressurise a boiler
The five-minute job that resolves more no-heating calls than any other. Here is how to do it properly, and how to tell when topping up is the wrong answer.Read the guideWhat to do when your condensate pipe freezes
The single most common winter boiler fault, and one of the few you can genuinely fix yourself in fifteen minutes with a kettle and some patience.Read the guideBoiler fault codes explained: what they actually tell you
Codes look like diagnoses and are not. Understanding which family a code belongs to turns a meaningless number into a genuinely useful starting point.Read the guide
Looking for Vaillant’s own support? www.vaillant.co.uk. We are not affiliated with Vaillant.