Written by Stephen Day
Gas Safe Engineer
Updated: 25th July, 2025
Error codes on boilers can be a confusing and frustrating topic, here at iHeat we want to make everything about boilers as straightforward as possible.
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In this blog we’ll be taking a look at the F62 error code displayed by Vaillant boilers, including - what it means, what causes it and how it can be fixed.
An error code is exactly as it sounds, an alphanumeric code (F62) displayed upon a boiler's control screen or window, usually found at the toe or in the centre of the boiler.
Error (fault) codes are displayed by a boiler when it senses either a function or component is not operating soundly, causing sub-optimal performance and in rare cases, health risks.
The F62 error code on Vaillant boilers indicates a problem with the gas valve. Specifically, it means that the gas valve has failed to open during the ignition sequence.
This can happen due to a variety of reasons, such as a fault with the gas valve itself, a problem with the wiring or connections to the gas valve, or a fault with other components in the ignition circuit.
The gas valve is responsible for regulating the flow of gas into a Vaillant boiler. When you require heating or hot water, the valve opens to allow gas to enter the boiler and ignite the burner.
However, if the valve remains open when the boiler is not in use, it poses a significant risk of a gas leak, which can be very dangerous.
Fortunately, Vaillant boilers are designed to trigger a ‘lockout’ (shut down) in the event of a faulty gas valve. If you see the F62 fault code on your boiler, you should immediately turn off the gas supply and contact a Gas Safe Registered engineer to address the issue.
Several factors can cause a faulty gas valve, including:
a faulty PCB that sends incorrect signals to the valve can cause it to open and close at the wrong time, leading to gas flowing through when not required and no gas when you need it.
an intermittent connection between the PCB and the valve would result in the same problems as the communication between components would cause heating system issues.
Your gas valve can become stuck due to wear and tear, this would result in the display of an F62.

As frustrating as it may seem, the F62 represents a serious fault with your boiler and it must be analysed and fixed by an expert, a Gas Safe registered engineer.
If there is a fault with your boiler's PCB it can seriously hinder the performance of your boiler and it could be worthwhile getting a newer model.
Other issues can be fixed by a qualified engineer more easily, but the most effective way of avoiding an F62 is by replacing any old boilers with a modern, efficient boiler. Modern boilers have been meticulously designed and expertly crafted for not only peak performance, but also product longevity.
Even if your current boiler is an antiquated system or showing no signs of wear and tear it can still be a good idea to upgrade.
New boilers can be a daunting purchase for many people as they’re an appliance with a lot of responsibility, providing heat for you and your family is something you want to get right. Boilers aren’t exactly a quickly disposable item either, potentially lasting you a decade.
Effectively, new boiler cost can be split into two segments: the first is the actual boiler itself (unit price), and the second is the cost of the boiler being installed (set up) in your property by an expert engineer.
Here at iHeat, we remove all of this undue stress and make the decision making process of upgrading to a new heating system, as easy as possible.
New boiler costs can vary depending on a number of factors including their brand, model, fuel, output, warranty, labour and boiler installation type. Typically a new boiler will cost between £1,845 and £3,500, below is a list of average boiler installations offered by iHeat (guide only).
Installation Type | Price (inc VAT) | |
Combi to combi swap | £1,845 | |
System to combi conversion | £2,499 | |
New boiler install | £2,899 | |
Back boiler to a combi | £3,299 | |
System to system | £1,945 |
Last updated: 25th July, 2025
Written by Stephen Day
Gas Safe Engineer at iHeat
Stephen Day is a Gas Safe registered and FGAS certified engineer with over 20 years of hands-on experience in the heating, cooling, and renewable energy industry, specialising in boiler installations, air conditioning, and heat pump systems.
LinkedInArticles by Stephen Day are reviewed by iHeat’s technical team to ensure accuracy and reliability.
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