Vaillant F62 Fault Code: Causes & What to Do

Vaillant F62 fault code? F62 means the boiler has detected that the flame did not switch off as quickly as expected after the burner was told to stop.

Vaillant lists the gas valve, PCB and ignition electrode as possible causes. Because this fault involves the boiler’s gas and flame-control system, it should be professionally diagnosed rather than investigated by removing the boiler casing.

The fault code does not automatically mean the gas valve or PCB needs replacing. Testing should confirm which component is actually responsible.

What Does the Vaillant F62 Fault Code Mean?

Vaillant describes F62 as:

The flame switch-off was detected after a delay.

During normal operation, the boiler opens the gas valve when heat is required and closes it when the burner needs to stop.

The flame should then extinguish correctly.

With an F62 fault, the boiler detects that this switch-off process has not happened as expected.

Depending on the Vaillant model, technical documentation may describe this as:

• delayed gas-valve switch-off;
• delayed extinguishing of the flame signal;
• a gas-valve control problem;
• an abnormal flame-monitoring condition.

The boiler can then enter lockout and display F62.

Vaillant F62 Fault Code: What Should I Do?

There is very little useful DIY troubleshooting for an F62 fault.

You can safely:

• write down the exact F62 code;
• note the Vaillant boiler model;
• record whether heating and hot water stopped;
• note whether another fault code appeared before F62;
• tell the engineer whether the fault is intermittent or happens every time.

Do not remove the boiler casing or attempt to test the gas valve, electrode or PCB yourself.

3 Possible Causes of a Vaillant F62 Fault

1. Gas Valve Fault

Vaillant lists a defective gas valve as one of the main possible causes of F62.

The gas valve controls gas entering the burner.

When the boiler stops calling for a flame, the valve should close correctly and the flame should extinguish.

If the valve does not close correctly or is allowing gas through when it should not, the boiler may detect delayed flame switch-off.

Vaillant’s professional fault-finding guidance recommends carrying out a local tightness test on the gas valve as part of diagnosing F62.

This is specialist gas work and must not be attempted by a homeowner.

Important diagnostic point: F62 does not mean “replace the gas valve”. The valve should be tested first.

2. PCB Fault

The printed circuit board, or PCB, controls many parts of the boiler’s operating sequence, including commands involving the gas valve and flame monitoring.

Vaillant also lists a defective PCB as a possible F62 cause.

However, the PCB should not automatically be replaced simply because F62 is displayed.

Vaillant’s professional guidance indicates that the gas valve should be checked first. If the valve is not allowing gas through incorrectly, the PCB may then become a stronger suspect.

This distinction matters because a PCB can be a significant replacement component.

For more information, see:

Boiler PCB Faults: Signs, Causes & Diagnosis

3. Ignition or Flame-Detection Electrode Fault

Vaillant’s current fault list also includes a defective ignition electrode as a possible cause of F62.

The electrode forms part of the boiler’s ignition and flame-monitoring system.

If the flame signal does not disappear correctly when the burner stops, the boiler may interpret this as delayed flame switch-off.

Model-specific technical guidance can therefore involve checking whether the problem is:

• a genuine delayed flame;
• a gas valve that is not shutting correctly;
• an incorrect flame signal;
• an electrode problem;
• a PCB fault.

This is why diagnosis needs to come before component replacement.

Does F62 Mean the Gas Valve Is Definitely Faulty?

No.

A gas-valve fault is one of the recognised F62 causes, but Vaillant also lists the PCB and ignition electrode.

The gas valve should be professionally tested before it is condemned.

If the valve passes the appropriate checks, the engineer may then need to investigate the PCB, flame detection and associated electrical components.

Does F62 Mean There Is a Gas Leak?

Not automatically.

F62 is an appliance fault indicating delayed flame switch-off. It does not by itself prove that gas is escaping into your home.

However, because the gas valve is one possible cause, the fault should be professionally investigated rather than ignored.

If you actually smell gas or suspect a gas escape, that is different from simply seeing F62 on the boiler display.

In Great Britain, call the National Gas Emergency Service immediately on 0800 111 999.

What Is the Difference Between Vaillant F27 and F62?

F27 and F62 can both involve flame detection or the gas valve, but they describe different conditions.

• F27: a flame signal is detected when the burner should already be off.
• F62: flame switch-off is detected after a delay.

The distinction can be subtle from a homeowner’s point of view, but it matters during fault diagnosis.

If your boiler displays F27, see:

Vaillant F27 Fault Code: Causes & What to Do

What Is the Difference Between Vaillant F61 and F62?

F61 and F62 are both associated with gas-valve control, but again they describe different detected problems.

F61 relates to the gas-valve control system and may involve the valve, wiring or electronics.

F62 relates specifically to delayed switch-off of the flame after the burner should stop.

An engineer should therefore use the exact fault code rather than treating all gas-valve-related faults in the same way.

Can a Faulty PCB Cause Vaillant F62?

Yes.

Vaillant officially lists a defective PCB as one possible cause.

However, because the PCB controls the gas valve and processes flame information, another fault elsewhere in that sequence can sometimes appear to involve the electronics.

The PCB should therefore be replaced only after the relevant checks have been carried out.

Can the Ignition Electrode Cause F62?

Yes. Vaillant’s current fault information includes a defective ignition electrode among the possible causes.

The electrode is involved in ignition and flame detection.

If the boiler continues to receive an incorrect flame signal after the burner should have stopped, the electrode or associated circuitry may need investigating.

This requires access inside the appliance and is not a homeowner repair.

Can Low Boiler Pressure Cause F62?

F62 is not a low-water-pressure fault.

Vaillant’s main low-pressure fault is F22.

If your boiler pressure is also low, mention it to the engineer because there may be a separate heating-system issue, but simply topping up the boiler is not the normal solution for F62.

For pressure problems, see:

Why Does My Boiler Pressure Keep Dropping?

Can I Reset a Vaillant F62 Fault?

Vaillant advises that F62 requires professional attention.

If the user manual for your specific boiler gives a normal reset procedure, record the fault code before following those instructions.

Do not repeatedly reset an F62 fault in an attempt to keep the boiler operating.

If the code returns, arrange diagnosis because the gas valve, PCB or flame-detection system may still have a fault.

Why Does Vaillant F62 Keep Coming Back?

If F62 clears temporarily but then returns, the underlying problem has probably not been resolved.

Useful information to give an engineer includes:

• whether F62 appears during heating or hot-water use;
• whether the boiler runs normally for a period first;
• whether another fault code appears before F62;
• whether the fault happens every time or intermittently;
• whether heating and hot water are both affected.

Intermittent faults can be especially useful to document because the appliance may appear normal when first inspected.

Can I Fix a Vaillant F62 Fault Myself?

No internal F62 repair should be attempted by a homeowner.

You can:

• record the code;
• identify the boiler model;
• note when the fault occurs;
• report any other fault codes;
• follow only normal user instructions for your boiler.

You should not:

• remove the boiler casing;
• test gas-valve tightness;
• adjust the gas valve;
• work on ignition electrodes;
• test live PCB connections;
• bypass the fault or safety controls.

How Is a Vaillant F62 Fault Diagnosed?

The engineer should determine whether the delayed flame switch-off is caused by the gas valve itself or by the boiler incorrectly detecting the flame.

Depending on the Vaillant model, diagnosis may involve checking:

• gas-valve operation;
• gas-valve tightness;
• the burner and flame switch-off sequence;
• ignition and flame-detection electrodes;
• electrical connections;
• the PCB;
• manufacturer-specific fault information.

Engineer point: Vaillant’s own professional guidance recommends checking the gas valve before moving towards PCB replacement.

How Much Does It Cost to Fix Vaillant F62?

There is no accurate fixed price for every F62 repair.

The eventual repair could involve:

• a gas valve;
• an ignition or flame-detection electrode;
• electrical connections;
• a PCB;
• another model-specific fault discovered during diagnosis.

These repairs differ significantly in parts cost and labour.

For that reason, the sensible approach is to diagnose the cause first and then price the confirmed repair.

Does F62 Mean I Need a New Vaillant Boiler?

No.

An F62 fault does not automatically mean the boiler needs replacing.

A confirmed gas-valve, electrode or PCB fault may be repairable.

Replacement becomes worth comparing if the appliance is older, has developed several expensive faults or the overall boiler condition makes another major repair difficult to justify.

If you are comparing the options, see:

New Boiler Cost Guide

What Should I Do If I Smell Gas?

Seeing F62 does not automatically mean gas is leaking into your property.

However, if you smell gas or suspect a gas escape, stop using the appliance.

Open doors and windows, avoid anything that could ignite the gas, and shut off the gas supply at the meter if you know how to do so safely.

In Great Britain, call the National Gas Emergency Service on 0800 111 999.

Do not use an appliance that you suspect is unsafe until it has been checked by a Gas Safe registered engineer.

When Should I Call a Boiler Engineer?

Arrange professional diagnosis if:

• F62 appears on your Vaillant boiler;
• F62 returns after a normal reset;
• the boiler repeatedly locks out;
• heating or hot water is unavailable;
• F27, F61 or another flame-related code also appears;
• you have been told the gas valve or PCB may be faulty.

For professional boiler fault diagnosis, visit:

Boiler Repairs

Vaillant F62 Fault in Cardiff?

If you’re in Cardiff and your Vaillant boiler is showing F62 or repeatedly locking out with a suspected gas-valve, PCB or flame-detection fault, visit:

Boiler Repair in Cardiff

When booking, tell us:

• the Vaillant boiler model;
• the exact F62 fault code;
• whether any other fault codes appear;
• whether the fault returns after resetting;
• whether heating and hot water are both affected;
• whether the problem is intermittent or happens every time.

Quick Questions

What does F62 mean on a Vaillant boiler?

F62 means the boiler detected delayed flame switch-off after the burner should have stopped.

What causes Vaillant F62?

Vaillant lists a defective gas valve, defective PCB and defective ignition electrode as possible causes.

Does F62 mean the gas valve is definitely faulty?

No. The gas valve is one possible cause, but the PCB and ignition electrode can also be responsible. The valve should be professionally tested before replacement.

Can a PCB cause F62?

Yes. Vaillant lists a defective PCB as a possible cause, but professional fault finding should check the gas valve and relevant flame-detection components before an expensive PCB is replaced.

Can an ignition electrode cause F62?

Yes. Vaillant’s current fault list includes a defective ignition electrode because an incorrect flame signal can affect how flame switch-off is detected.

Is Vaillant F62 dangerous?

F62 involves the boiler’s flame and gas-valve shut-off system, so it should not be ignored or bypassed. Vaillant advises professional attention rather than homeowner repair.

Does F62 mean there is a gas leak?

Not automatically. F62 is a boiler fault code. If you actually smell gas or suspect a gas escape, call the National Gas Emergency Service on 0800 111 999.

Need Help With a Vaillant F62 Fault?

Let’s Heat can diagnose Vaillant F62 faults, recurring lockouts and suspected gas-valve, PCB and flame-detection problems.

You do not need to identify the failed component yourself before booking.

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Sources Checked

This guide has been checked against current Vaillant fault-code information, Vaillant professional fault-finding guidance and HSE gas-safety guidance.

Vaillant – Official Boiler Fault Codes

Vaillant Professional – Fault-Finding Guidance

HSE – Gas Safety for Homeowners