What does Vaillant fault code F.28 mean?

F.28 is an ignition fault. The boiler attempted to light but failed to detect a flame. Causes include low gas pressure, faulty ignition electrode, blocked burner, or defective flame detection. Requires a Gas Safe engineer.

What does Vaillant fault code F.75 mean?

F.75 means no pressure change detected at start. The pump activates but the pressure sensor does not detect a change. Usually a faulty pressure sensor or pump. Requires a Gas Safe engineer.

What does Vaillant fault code F.22 mean?

F.22 is low water pressure. System pressure has dropped below 0.5 bar. Re-pressurise to 1.0-1.5 bar using the filling loop. If pressure drops repeatedly, an engineer should investigate for a leak.

What does Vaillant fault code F.29 mean?

F.29 indicates the flame was detected then lost during operation. Causes include gas supply interruption, faulty gas valve, or ignition issues. Requires a Gas Safe engineer.

What does Vaillant fault code F.62 mean?

F.62 is a safety gas valve relay check failure. This is a safety lockout requiring a Gas Safe engineer to inspect the gas valve and associated controls.

What does Vaillant fault code F.83 mean?

F.83 indicates a flue gas temperature sensor fault or no temperature rise detected. Causes include a blocked heat exchanger, faulty sensor, or combustion issue. Requires a Gas Safe engineer.

What does Vaillant fault code F.20 mean?

F.20 is a high temperature safety shutdown. The boiler detected an abnormally high flow temperature. Causes include blocked heat exchanger, restricted circulation, or faulty pump. Do not restart repeatedly - contact a Gas Safe engineer.

What does Vaillant fault code F.73 mean?

F.73 indicates a water pressure sensor fault — the sensor is sending an implausible or out-of-range reading. Unlike F.22 (low pressure), this cannot be resolved by re-pressurising. A Gas Safe engineer is required to test and replace the pressure sensor.

What is the difference between an F-code and an S-code on a Vaillant boiler?

F-codes indicate a fault that has caused the boiler to lock out or shut down. S-codes indicate the current operating status such as heating active, hot water demand, or standby mode. S-codes are generally informational and do not indicate a fault.

How do I reset my Vaillant boiler after a fault code?

Press and hold the reset button on your Vaillant boiler for approximately 3 seconds. If the fault code returns after reset, do not continue to reset the boiler repeatedly - contact a Gas Safe registered engineer to diagnose the underlying cause.

Fault Code Guide

Vaillant Fault Code Guide — Every F-Code & S-Code Explained

Complete reference for all Vaillant boiler error codes — F-codes (faults) and S-codes (status). Vaillant ecoTEC error codes explained. Find your code, understand the cause, and get it fixed.

Free download: The Vaillant owner’s guide to fault codes & when to replace — by email, no booking needed. Get the free guide

No codes match your search.
Try a different code or keyword, or book an engineer to diagnose your boiler.

Can't find your code or need help now?

Our Gas Safe engineers carry the most common Vaillant parts on their vehicles for first-visit fixes.

Emergency Vaillant Repairs Book a Vaillant Boiler Service