This fault can involve incomplete combustion and carbon monoxide.
If anyone in the property feels sick, dizzy or drowsy, or you can smell gas: open the windows, leave the building, and do not switch anything on or off. Then call the National Gas Emergency Service.
0800 111 999Vaillant F.62 fault codewhat it means and how to fix it
The gas valve is not shutting off when the boiler tells it to. This is a gas safety fault and the boiler must not be used until an engineer has seen it.
Stop — this needs an engineer
Get a Gas Safe registered engineer to look at your Vaillant F.62
We do not pass enquiries to a repair firm, so there is no form here. Find a Gas Safe registered engineer through the Gas Safe Register, and ask to see their registration card when they arrive — it is the register, not the van, that tells you they are qualified.
What F.62 means
F.62 means the control board commanded the gas valve to close and did not see it close within the expected time. The board monitors this every cycle, because a gas valve that closes slowly or not at all is the single most serious failure mode a domestic boiler has. It means gas can continue to flow after the burner should have stopped. The boiler locks out and refuses to operate, and that lockout should be left in place. There is nothing a householder can check here. Do not reset it more than once, and if it returns, turn the appliance off and leave it off until it has been repaired.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Faulty gas valve | The valve mechanism is slow to close or is not closing fully. Replacement is the only remedy and it is a gas-qualified job. | Common |
| Control board fault | The board is commanding correctly but misreading the valve feedback, or is failing to send the shut-off signal at all. | Occasional |
| Damaged wiring to the gas valve | A chafed or corroded connection between the board and the valve. Found by inspection during diagnosis. | Rare |
Can you fix it yourself?
Stop — this needs an engineer
What it costs to fix
Typical repair cost
£280–£450
Time on site
2 hours
Gas valve replacement £280–£450 including the mandatory combustion check afterwards. Control board, if that is the cause, £320–£520.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Parts you may need
We may earn a commission if you buy a part through one of these links. It does not change what you pay, and it does not affect which parts we list.
Vaillant ecoTEC gas valve
0020053968£110–£210Authorised Vaillant parts distributor
Price checked 28 September 2026
Own this appliance and had this code? . Nothing is published until a person has read it.
Related Vaillant fault codes
- F.61Get it checkedThe gas valve control circuit has faulted. The boiler will not fire and this is firmly an engineer's job.Related: gas valve and supply
- F.53Get it checkedThe gas is not flowing through the valve the way the boiler expects. Vaillant's list runs from low gas pressure to a wet or blocked filter under the venturi cap.Related: gas valve and supply
- F.54Get it checkedA gas supply fault, usually shown alongside F.28 or F.29. It means gas is reaching the appliance at too low a pressure.Related: gas valve and supply
- F.26Get it checkedVaillant call this "fuel valve not working": the stepper motor that drives the gas valve is not responding, so the boiler cannot open the gas and will not light.Related: gas valve and supply
- F.42Get it checkedA fault with the coding resistor, the small component that tells the board which gas the boiler is set up for. The boiler will not run until it knows.Related: gas valve and supply
- F.88Get it checkedThe board cannot see the gas valve. Vaillant print F.88 as the valve not connected or connected incorrectly, or a harness fault, and the boiler will not run until the circuit is proved.Related: gas valve and supply
Own a Vaillant boiler? Save it and its codes come first next time.
Related guides
Common questions about Vaillant F.62
Can I use the boiler until the engineer arrives?
No. Turn it off at the front panel and leave it off. This code specifically indicates that the component responsible for stopping the gas is not behaving as it should, and that is not a fault to work around for a few days.
Should I turn the gas off at the meter?
If you can do so easily and you are not leaving other essential appliances without gas, it is a reasonable precaution. If you can smell gas at any point, leave the property and call 0800 111 999 rather than investigating.
How much does a gas valve cost to replace?
Typically £280 to £450 fitted on a Vaillant ecoTEC, including the combustion analysis that must follow. On a boiler over twelve years old it is worth asking whether that money is better put toward replacement.
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
- Trade body guidance
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.