Vaillant F62 fault code: flame switch-off delay explained

What does the Vaillant F62 fault code mean?

The Vaillant F62 fault code means the control system detected the flame switch-off after a delay: in plain English, the gas valve isn't opening and closing in the correct timing window relative to the flame, so gas may still be flowing fractionally too long after the flame goes out. Because this touches the boiler's gas-safety logic, it locks the boiler out rather than letting it keep running.

Vaillant's own fault-code page defines F62 as “the flame switch-off was detected after a delay”, and lists a defective gas valve, a defective PCB or a defective ignition electrode as the possible causes. It appears across the ecoTEC range, including the ecoTEC plus and ecoTEC pro models.

Key facts

The quick version, before the detail.

• Meaning: a delay switching off the gas valve after the flame goes out (Vaillant's official wording).
• DIY-fixable? No. A single reset and a few basic checks are safe; every likely cause needs a Gas Safe registered engineer.
• Gas Safe job if: the fault persists after one reset, or you're not confident the checks are safe to make.
• Seen on: the Vaillant ecoTEC range, including the ecoTEC plus and ecoTEC pro models.
• Smart Plan boiler & central heating cover: parts and labour up to £500 a year if the boiler is under 7 years old, or up to £200 a year if it is over 7.
• A £95 call-out fee, paid in advance, applies in your first 30 days, for faults the plan does not cover, if the engineer cannot get access, and for early annual-service requests.
• Cover-plan call-outs run Monday to Friday, 08:00 to 18:00. Outside those hours you are only seen sooner for a genuine emergency breakdown, so a Friday-evening or weekend fault can wait until Monday.
• Using a module starts a 12-month agreement period the first time you use a service. There is a 14-day cooling-off period, but it ends once a service is carried out, and leaving early after that costs the remaining months or 75% of the outstanding balance.

Why does the F62 code appear?

F62 points at the timing between the gas valve closing and the flame going out, so the likely causes sit around the valve, the printed circuit board that controls it, and the ignition electrode that detects the flame. Repair engineers commonly report the circuit board behind the fault more often than any other single cause, with a faulty gas valve the next most frequent finding.

The table below runs through the likely causes, what you might notice, and who can safely deal with each one.

F62 causes and who fixes them

Can I fix a Vaillant F62 myself?

There's very little you can safely check yourself with F62, and none of it involves opening the boiler casing or touching the gas valve, PCB or ignition electrode. Work through the steps below, in order, and stop if you smell gas.

1. If you smell gas, don't reset the boiler. Turn off the gas supply, ventilate the room, and call the National Gas Emergency Service on 0800 111 999 straight away.

2. Check your other gas appliances. If they're working fine, the fault is specific to the boiler rather than the wider gas supply.

3. Take a look at the flue outside, if you can see it safely, for anything obviously blocking it.

4. Reset the boiler once, following the steps in your Vaillant manual. The reset button is Vaillant's own suggested first step, not something to be wary of.

Stop there. If F62 comes back after a reset, that points to a hardware fault rather than a one-off glitch, and repeating the reset won't fix it. Book a Gas Safe registered engineer to check the gas valve, PCB and ignition electrode rather than resetting again.

Is F62 the same as F61?

No. F62 and F61 are both part of Vaillant's ignition and flame-timing family of fault codes, but they're distinct faults and shouldn't be treated as interchangeable. If your boiler has shown F61 as well, don't assume it means the same thing as F62; our Vaillant F61 guide covers that code on its own terms.

Either way, the same principle applies: these are safety lockouts, not codes to keep clearing with repeated resets. If the fault returns, it needs a Gas Safe registered engineer to look at the gas valve, PCB and ignition electrode.

When to call a Gas Safe registered engineer

Because every likely cause of F62 sits behind the boiler casing, a Gas Safe registered engineer is the right call as soon as the fault comes back after one reset. That's specialist, legally restricted work covering the gas valve, the PCB and the ignition electrode, not a DIY job.

You can book a one-off repair with us and a Gas Safe registered engineer will come and fix it, or call us on 0333 772 6247. A Smart Plan boiler and central heating module covers parts and labour up to £500 a year if your boiler is under 7 years old, or up to £200 a year if it's over 7. Cover is modular, so you only pick what you want.

A few things worth knowing before you set up cover. A £95 call-out fee, paid in advance, applies in your first 30 days, for faults the plan doesn't cover, if the engineer can't get access, and for early annual-service requests. Cover-plan call-outs run Monday to Friday, 08:00 to 18:00; outside those hours you're only seen sooner for a genuine emergency breakdown as set out in your terms, so a fault on a Friday evening or over the weekend can wait until Monday. And using any module starts a 12-month agreement period from the first time you use a service; there's a 14-day cooling-off period, but it ends the moment a service is carried out, and leaving early after that costs the remaining months or 75% of the outstanding balance.

Smart Plan is a service plan, not insurance. In plain terms, it's a membership that arranges and funds covered repairs up to the limits on your plan, rather than a regulated financial product; it doesn't pay out a cash sum, and cover is limited to the modules you've chosen and the limits set out in your terms. It's provided by UK Boiler Company Ltd, which has traded since 2014 and looked after over 15,000 customers.

One safety note: if you ever smell gas or suspect carbon monoxide, don't wait for an engineer; call the National Gas Emergency Service on 0800 111 999 straight away.

Vaillant F62 fault code FAQs

Seeing F62? We'll come and fix it for you.

Book a one-off repair and a Gas Safe registered engineer will check the gas valve, PCB and ignition electrode, or set up a Smart Plan boiler and central heating module so covered repairs are handled up to your cover limit: up to £500 a year for a boiler under 7 years old, or up to £200 a year if it's older. It's a service plan, not insurance, so it funds covered repairs rather than paying out a cash sum. A £95 call-out fee, paid in advance, applies in your first 30 days, for faults the plan doesn't cover, no-access visits and early annual-service requests. Cover-plan call-outs are Monday to Friday, 08:00 to 18:00 unless it's a genuine emergency. Using a module starts a 12-month agreement period once you first use a service; leaving early costs the remaining months or 75% of the outstanding balance.

Helpful links

• All Vaillant fault codes
• Vaillant F61 fault code
• Vaillant fault code help
• Boiler not working? Book a repair
• Boiler & central heating cover
• Vaillant official fault-code list
• Check an engineer on the Gas Safe Register