How to Fix the Vaillant F62 Fault Code

If your Vaillant boiler is showing the F62 fault code, it usually means the gas valve has failed to close fully after the burner should have switched off. The boiler detects gas flow at a point when there shouldn't be any, and locks out as a safety measure — this is different from F61, which relates to the valve failing to open.

While some simple checks are safe, repairs involving gas components should always be carried out by a Gas Safe registered engineer.

If you're unsure what another error means, see our guide to Vaillant boiler fault codes for explanations of the most common faults.

What Does the Vaillant F62 Fault Code Mean?

The Vaillant F62 fault code is a delayed flame switch-off fault. It indicates that the gas valve took too long to close, or failed to close, after the burner turned off.

The fault may be caused by:

• Faulty gas valve that isn't closing properly
• Wiring or electrical connection faults between the PCB and gas valve
• PCB faults sending incorrect signals to the valve
• Worn ignition electrode affecting the combustion and flame-detection sequence

You may also see related faults such as F28, F29 or F75 depending on the underlying issue.

Which Vaillant Models Commonly Show the F62 Fault?

The F62 fault is most often reported on older Vaillant ecoTEC Plus and ecoTEC Pro R1 boilers. As these boilers age, components such as the gas valve and PCB become more prone to wear.

What Causes the Vaillant F62 Fault Code?

Common causes include:

• A gas valve that isn't closing fully or promptly.
• PCB faults affecting communication with the gas valve.
• A worn ignition electrode sending an inaccurate flame signal.
• Wiring faults between the PCB and gas valve.

All of these require proper diagnosis before parts are replaced.

Why Does the Gas Valve Fail to Close?

The gas valve itself may not always be the root cause. Common reasons include:

• Mechanical wear causing the valve to stick partially open.
• A faulty PCB sending incorrect closing signals.
• Poor or intermittent PCB connections.

Correct testing is needed to identify which component has failed.

How to Fix the Vaillant F62 Fault Code

Before arranging a repair you can safely:

• Check the boiler has a gas supply.
• Confirm the gas isolation valve is open.
• Reset the boiler once.

Do not remove the boiler casing or attempt to test gas components yourself.

If the fault returns, a Gas Safe engineer should test the gas valve, wiring and PCB before replacing any parts. If the fault keeps returning, it's best to arrange a boiler repair service in London with a Gas Safe engineer.

Keeping up with annual servicing also helps identify developing faults before they lead to breakdowns.

Why Does the F62 Fault Come and Go?

Many homeowners notice the boiler works normally after a reset before the F62 code returns.

This intermittent behaviour is common on ageing boilers where the gas valve or PCB is beginning to fail. As the fault worsens, resets usually become less effective.

Should You Repair or Replace Your Boiler?

If your boiler is over 10 years old and repeatedly develops PCB or gas valve faults, replacement may be the more economical option.

For newer boilers, repairing the faulty component is often worthwhile if the rest of the appliance is in good condition.

An engineer can advise whether repair or replacement offers the better long-term value.

Does a Vaillant Warranty Cover an F62 Fault?

A Vaillant warranty may cover repairs where the fault is due to a manufacturing defect and the warranty remains valid.

Annual servicing by a Gas Safe registered engineer is normally required to maintain warranty cover. Always check the terms of your specific warranty.

Need Help with an F62 Fault?

If your Vaillant boiler keeps showing the F62 fault code, our Gas Safe engineers can diagnose the fault, identify whether the issue is the gas valve, PCB or another component, and carry out the necessary repair.

We provide boiler repairs across London.