How to Fix Vaillant F61 Fault Code: Causes and Step-by-Step Solutions
If your Vaillant boiler shows F61, your boiler has stopped for a safety reason. This fault points to a gas valve actuation/control problem. In plain English, the boiler’s electronics cannot control the gas valve correctly, so the boiler locks out to protect you.
Vaillant F61 fault code means the boiler cannot actuate (control) the gas valve. The most common causes include a faulty gas valve, a wiring harness/connection issue, or faulty electronics/PCB. You can try a safe reset and basic supply checks, but you should arrange a Gas Safe engineer because this fault involves a safety-critical gas component.
Table of contents
What is the Vaillant F61 Fault Code?
On many Vaillant ecoTEC models, F.61 = “Fuel/Gas valve actuation”. Vaillant manuals describe it as a fault where the gas valve assembly cannot be actuated, and they point to likely causes such as:
- Short circuit / short to earth in the wiring harness to the gas valve
- Gas valve assembly defect (for example, coils shorted to earth)
- Electronics/PCB defect
That’s why Google AI summaries often mention gas valve + PCB/control together.
Is Vaillant F61 dangerous?
Treat F61 as urgent, because it relates to gas valve control (a safety-critical function). Don’t try internal repairs, don’t remove the boiler case, and don’t keep forcing resets to “make it run.” Get a Gas Safe engineer to diagnose it properly. UK law also requires Gas Safe registration for gas work.
If you smell gas or suspect a leak
Call the National Gas Emergency Service: 0800 111 999 and follow their safety steps (ventilate, avoid electrical switches, etc.).
Common Causes of Vaillant F61 Fault Code
Understanding the cause is essential before attempting any fix. The F61 fault code usually arises from:
- Faulty Gas Valve – A stuck or malfunctioning gas valve can prevent the boiler from igniting.
- Gas Supply Issues – Blockages or low gas pressure can stop the valve from receiving enough fuel.
- Wiring Problems – Loose connections between the PCB (printed circuit board) and the gas valve can trigger the fault.
- PCB Faults – A defective PCB can fail to send proper signals to the gas valve.
- Electrical or Component Failures – Malfunctions in the ignition lead, electrodes, sensors, or other boiler components can also cause the error.
Step-by-Step Guide to Fix Vaillant F61 Fault Code
Time needed: 5 minutes
Here’s a practical approach to resolving the F61 fault code:
- Turn Off the Boiler
Switch off your boiler completely and ensure the gas supply is uninterrupted. This prevents further strain on the system.
- Check the System Pressure
Low pressure can mimic an F61 error. Check the pressure gauge and ensure it’s in the recommended range (usually 1–1.5 bar).
- Inspect the Gas Supply
Make sure the gas flue isn’t blocked and that gas is flowing properly to the boiler. Any interruption can trigger the fault code.
- Reset Your Boiler
Sometimes, a simple reset can restore normal function: Turn off the boiler. Wait 5 minutes. Turn it back on.
- Bleed the Radiators
Air trapped in the system can cause pressure fluctuations leading to an F61 error. Bleeding your radiators can help stabilize the system.
- Call a Professional for Advanced Fixes
If the boiler still shows F61:
Have a Gas Safe engineer inspect the gas valve for damage or irregular operation. Consider a full boiler service to check sensors, electrodes, and the PCB. Replace any faulty components as recommended by the engineer.
Can I keep using the boiler if it resets?
If the boiler resets and runs, you might feel tempted to leave it. Don’t. F61 often returns because the underlying issue remains. Treat a repeat F61 as a clear sign to book an engineer.
How to Prevent Vaillant F61 Fault Code
Preventive measures can reduce the risk of encountering this fault code:
- Regular Maintenance – Schedule annual servicing to ensure all components, including the gas valve, are functioning correctly.
- Monitor Your Boiler – Pay attention to unusual noises, delayed ignition, or irregular heating. Early detection can prevent major issues.
When to Call the Professionals
While basic troubleshooting can help, you should always call a Gas Safe registered engineer if:
- The F61 fault persists after a reset.
- You notice any gas leaks or smell gas.
- Components like the gas valve or PCB are suspected to be faulty.
Conclusion
The Vaillant F61 fault code is a serious but manageable issue. By understanding its causes and following the step-by-step troubleshooting guide, you can often identify minor problems yourself. For more complex issues involving gas valves, PCB faults, or other components, always rely on a Gas Safe registered engineer.
Frequently Asked Questions
No. You can do safe external checks and a single reset, but the actual diagnosis and repair requires a Gas Safe engineer.
Not always. F61 points to gas valve control/actuation, not automatically a leak. If you smell gas, treat it as an emergency and call 0800 111 999.
Sometimes it clears briefly, but many cases return because the root cause remains (wiring, valve, PCB).
F62 appears when your Vaillant boiler detects an abnormal flame shut-down. Vaillant links it to components involved in safe combustion control – gas valve, PCB, ignition electrode. Know about Vaillant F62 Fault in detail.
