Vaillant F62 Fault Code: What It Means and What to Do

What does F62 mean on a Vaillant boiler?

On a Vaillant boiler — typically the ecoTEC range — the F62 fault code means a delayed flame switch-off, sometimes described as a gas valve shut-off delay. In normal operation, when the burner is meant to switch off, the gas valve closes and the flame extinguishes almost instantly.

With F62, the boiler's control board still detects a flame signal after the gas valve should have closed. Because that suggests gas may not be shutting off cleanly, the boiler deliberately locks out to keep things safe.

This is a protective code, not a nuisance one. It is the boiler's safety logic doing exactly what it should: stopping operation when it cannot confirm the gas valve has shut off properly.

The fault almost always sits in the gas valve, the printed circuit board (PCB), or the ignition/flame-sensing electrode — all sealed, gas-side or electronic components that only a qualified engineer should touch.

Common causes of F62

F62 has a fairly narrow list of likely causes, and most point to ageing internal parts:

• A faulty PCB (control board) — on older ecoTEC boilers this is one of the most common causes. The board misreads or mistimes the flame signal and trips the fault.
• A failing or leaking gas valve — if the valve is slow to close or not seating properly, the flame lingers and triggers F62.
• A faulty ignition/flame-sensing electrode — a worn or fouled electrode can send an incorrect flame signal back to the board.
• Wiring or connection faults between the board, electrode and gas valve.

Because the symptoms overlap, an engineer has to test rather than guess. In practice, the PCB and gas valve account for the large majority of F62 call-outs on older Vaillant boilers.

What you can safely check

F62 leaves very little for a homeowner to do safely — and that is the right outcome for a gas-side fault. The universal safe checks are the limit of DIY here:

1. Try one reset. Press and hold the reset button as described in your manual, or see our guide on how to reset your boiler. If F62 clears and does not return, it may have been a one-off glitch. If it comes straight back, stop — do not keep resetting, as repeatedly clearing a genuine safety lockout is not safe.
2. Check the gas is on. Make sure the gas supply isn't isolated and that other gas appliances are working. If you smell gas at any point, leave the boiler alone and call the National Gas Emergency line on 0800 111 999.
3. Glance at the pressure gauge. While F62 isn't a pressure fault, it's worth knowing your normal cold pressure (around 1.0–1.5 bar). See what your boiler pressure should be if you're unsure.

That is the full extent of safe homeowner action for F62. Do not open the casing, touch the gas valve, electrode or PCB, or attempt any internal work — all of it is sealed, gas-side or electronic and reserved for a registered engineer.

When to call a Gas Safe registered engineer

If F62 returns after a single reset, that is your trigger to call a Gas Safe Register engineer. Repairing a gas valve, PCB or flame electrode is gas-side work, and it is both illegal and dangerous for an unregistered person to attempt it.

When the engineer arrives, they will typically:

• Read the fault history and live data from the boiler's diagnostics.
• Test the gas valve operation and check it closes correctly.
• Inspect the ignition/flame-sensing electrode and its wiring.
• Check the PCB for faults and confirm whether the board, valve or electrode is at fault.
• Replace the failed component and verify the boiler shuts off cleanly with no lingering flame signal.

Because the symptoms are similar, the engineer may need to substitute or test parts to isolate the cause — which is exactly why diagnosis is best left to a professional. This is closely related to a faulty gas valve and the boiler's lockout behaviour, both of which an engineer will work through methodically.

Typical Vaillant F62 repair cost

Costs depend heavily on which part has failed. The PCB and gas valve are the most expensive outcomes; a simpler electrode or wiring fix sits at the lower end. The figures below are indicative 2026 UK ranges including parts and labour — your engineer will confirm after diagnosis.

Work involved	Indicative 2026 cost
Diagnostic / call-out	£70–£120
Ignition/flame electrode replacement	£100–£180
Gas valve replacement (parts + labour)	£200–£340
PCB replacement (parts + labour)	£300–£560

On older boilers, a PCB replacement that approaches the cost of a budget new boiler can tip the decision toward replacement — worth weighing if the appliance is well over a decade old. For broader context, see our guide to boiler repair costs.

Related Vaillant codes

If you're troubleshooting a Vaillant, these sibling guides may help — or browse the full Vaillant fault codes hub:

• Vaillant F28 — ignition failure (boiler won't fire up).
• Vaillant F29 — flame lost shortly after ignition.
• Vaillant F22 — low water pressure / dry fire.

Will boiler cover pay for an F62 repair?

Often, yes — but it depends on your policy, and the following is general information rather than financial advice. Many boiler cover plans include parts and labour for breakdowns like a failed gas valve or PCB, which is exactly what F62 usually comes down to.

The common catches are: a policy excess, an exclusion for boilers over a certain age, and an initial exclusion period when you first take out cover. A PCB on an older boiler can also bump up against any "uneconomical to repair" clause.

It's worth reading the small print before assuming F62 is covered. Our guides on what boiler cover includes and whether boiler cover is worth it walk through the typical exclusions and how to judge value for your boiler's age and condition.

This article is general information, not gas-safety or financial advice. Always have gas appliances checked and repaired by a Gas Safe registered engineer. In a gas emergency, call the National Gas Emergency line on 0800 111 999. Costs are indicative UK guides for 2026.