How to Fix Vaillant F62 Fault Code: Causes and Step-by-Step Solutions

Vaillant F62 Fault Code means the boiler detected a delayed flame switch-off. Vaillant lists likely causes as a faulty gas valve, faulty PCB, or faulty ignition electrode, and advises this is a job for an engineer (do not open the casing).

What is the Vaillant F62 Fault Code?

F62 appears when your Vaillant boiler detects an abnormal flame shut-down (“flame switch-off … after a delay”). Vaillant links it to components involved in safe combustion control – gas valve, PCB, ignition electrode – so you should not treat it as a “minor glitch.”

This issue can occur alongside other fault codes like F28, F29, or F75, all of which are related to the gas system.

Is Vaillant F62 dangerous?

F62 relates to the combustion/control side of the boiler. That area needs Gas Safe-level diagnosis, not DIY. Vaillant explicitly tells homeowners not to open the casing and to arrange an engineer for this code.

UK guidance also requires a Gas Safe registered engineer for gas work in domestic properties. If you smell gas: stop and follow gas emergency guidance immediately.

Common Causes of Vaillant F62 Fault Code

Several factors can trigger the F62 error:

1. Faulty Gas Valve
   • The gas valve may fail to open or close correctly due to wear and tear, preventing gas from reaching the burner.
2. Faulty Gas Pressure Sensor
   • A malfunctioning sensor may send incorrect readings, causing the boiler to shut down.
3. Blocked Gas Supply
   • Debris in the gas line or a faulty gas meter can limit the gas supply, triggering the fault.
4. Low Gas Pressure
   • Gas leaks or pressure regulator issues can reduce system pressure, causing boiler shutdown.
5. Faulty PCB (Printed Circuit Board)
   • The PCB controls signals to the gas valve. A faulty or intermittently connected PCB can result in F62 errors.
6. Stuck Gas Valve
   • Over time, mechanical issues can prevent the valve from regulating gas flow correctly.

What to do right now (user-level checks only)

Do these in order. Keep it simple.

1) Check your gas supply

• Confirm other gas appliances (hob/cooker) work.
• If you use a prepay meter, check credit.
• Vaillant recommends checking gas availability when ignition/combustion issues occur.

2) Check power and controls

A power interruption or control setting can stop ignition and trigger faults. Confirm:

• Boiler isolation switch is ON
• No tripped fuse
• Thermostat calls for heat (set above room temp)

3) Do ONE reset (don’t spam resets)

Vaillant states that resetting can sometimes clear a fault or restore heat temporarily, but the F62 page still routes you to an engineer for proper resolution. If the fault returns, stop and book an engineer.

Step-by-Step Fix for Vaillant F62 Fault Code

Why Does the F62 Fault Happen Intermittently?

The F62 code often appears in boilers older than 10 years. Wear and tear on the gas valve or PCB can cause the boiler to fail randomly. You may notice:

• Cold showers
• Boiler temporarily shutting down
• Error code appearing, then disappearing after a reset

This intermittent fault usually indicates that replacement parts are needed rather than a simple reset.

How to stop F62 coming back

You can’t “prevent” an F62 with a trick. You reduce risk with basics:

• Book servicing and safety checks. Gas Safe advises contacting a registered engineer if your boiler does not function as expected. Here is Vaillant Help and Support
• Don’t ignore repeated resets. Vaillant warns against DIY casing access and routes fault codes like F62 to engineers for a reason.

Conclusion

The Vaillant F62 fault code is a clear signal that your boiler’s gas system needs attention. While some issues can be checked at home, most fixes such as replacing the gas valve, sensor, or PCB require a qualified Gas Safe engineer for safety and compliance. Regular servicing and timely repairs can prevent recurring faults and extend the life of your boiler.

Frequently Asked Questions