Vaillant Boiler Fault Codes & Manuals

When your Vaillant boiler shows a fault code, it’s the system’s way of alerting you that something isn’t working as it should. Each code points to a specific issue — from ignition failures and low pressure to fan or sensor problems.

Use the list below to look up your Vaillant boiler fault code and find out what it means. You’ll also see what you can safely check yourself, and when it’s time to call a Gas Safe engineer for professional help.

These codes cover the most popular Vaillant ranges, including the ecoTEC Plus, ecoFIT Pure, ecoTEC Pro, and turboTEC models. If your boiler isn’t listed, scroll down to download the official Vaillant manual for your model.

Remember: resetting your boiler once is fine, but if the same code returns, always get it checked by a qualified engineer.

⚙️ Common Vaillant Boiler Fault Codes

F22 – Low Water Pressure
The boiler pressure is too low, often below 1.0 bar. Top up your system using the filling loop until it reads around 1.2–1.5 bar. If the pressure keeps dropping, you may have a leak or expansion vessel issue.

F28 – Ignition Failure (No Flame Detected)
The boiler tried to light but failed. Check that your gas supply is on and credit meters have balance. You can reset the boiler once. If the code returns, contact a Gas Safe engineer — the ignition or gas valve may need attention.

F29 – Flame Extinguished During Operation
The flame started but then went out. Causes include gas pressure problems, blocked flue, or condensate issues. Reset once; if the code comes back, call an engineer.

F75 – Pump or Pressure Sensor Fault
The boiler can’t detect pressure changes when the pump runs. Bleed radiators, top up pressure, and try a reset. If it still shows F75, a sensor or pump check is needed.

F27 – False Flame Detection
The boiler’s system has detected a flame when it shouldn’t. This is usually a sensor or PCB issue. Call an engineer to inspect safely.

F62 – Gas Valve Fault
A delay or malfunction in the gas valve. Do not attempt any DIY fix — call a Gas Safe engineer immediately.

F83 – Flow Temperature Rise Too Slow
The boiler is struggling to circulate hot water. Check system pressure and radiators. Engineer may need to check the pump or sensors.

F84 / F85 – Flow and Return Sensor Faults
The sensors that monitor water temperature may be reading incorrectly or disconnected. Engineer visit required.

F61 – Gas Valve Electrical Fault
A control or wiring issue affecting the gas valve. Turn off the boiler and book a professional inspection.

F33 – Fan / Air Pressure Fault
The fan isn’t running correctly or the air pressure switch has detected an issue. Engineer attention needed — don’t use the boiler until checked.

🔩 Most Common Codes by Range

• ecoTEC Plus & Pro: F22 (Low pressure), F28/F29 (Ignition faults), F75 (Pump/sensor)

• ecoFIT Pure: F28 and F83 most common

• turboTEC: F22 and F27 frequently seen on older models

⚠️ Safety Reminder

Always switch off your boiler and call a Gas Safe engineer if you smell gas, hear unusual noises, or see repeating fault codes.
Only perform simple checks like repressurising or resetting once — never remove covers or parts yourself.