Vaillant Boiler F68 Fault Code
The Vaillant fault code F68 - Circuit board problems Q & A, this is normal related to an electrical issue and if you require an engineer for an emergency boiler repair, feel free to use our service.
The Vaillant Boiler Fault Code F68 Error Common Q&A
Vaillant Boiler F68 Fault Code
- What does the F68 fault code mean on my Vaillant boiler?
- What has caused the fluctuation in flame signal?
- How can the issue causing the F68 fault code be narrowed down?
- Can I fix the F68 fault without a gas engineer?
- How will the gas engineer know if low inlet gas pressure is the problem?
- What if the meter is supplying gas at the right pressure?
- What can we do if the problem causing the F68 fault code lies with the gas valve?
- What happens if the gas valve fails?
- How much does it cost to fit a gas valve, and how long will it take?
- What issues can arise with the flue on my Vaillant boiler?
- How can a blockage in a flue cause the Vaillant F68 fault code to be displayed?
- How would the burner contribute to the F68 fault code being displayed?
- What’s the fix for a burner that’s not running correctly?
- What can cause the electrode, ignition lead or spark generator to cause the F68 fault?
- What else can lead to a F68 fault on my Vaillant boiler?
- Can an engineer check to see if the PCB is at fault?
What does the F68 fault code mean on my Vaillant boiler?
According to Vaillant, the F68 fault code on your boiler is due to a problem with the flame signal.
The boiler’s PCB (the circuit board that controls the boiler) needs to see a signal for a strong flame. If it doesn’t, it highlights a potential problem.
A fluctuation of flame signal (depending on its severity), can lead to a boiler lockout and the F68 fault code being displayed.
What has caused the fluctuation in flame signal?
Unfortunately, this isn’t a particularly precise fault code.
Whilst the reason behind the lockout is precise (flame signal issue), what’s caused it could be many things, including:
- The inlet gas pressure to the boiler is low or fluctuating
- Adjustment on the gas valve is incorrect, or the gas valve is faulty
- There is a problem with, or blockage in the flue
- The burner is blocked with debris
- Ignition leads and electrode failure
- The spark generator is faulty
How can the issue causing the F68 fault code be narrowed down?
Some newer boilers will display multiple fault codes. If this is the case with your boiler, the crossover in what the fault codes mean, can help determine what is causing the fault.
Alongside this, make sure you inform your gas engineer of any oddities you’ve noticed with your boiler’s operation.
This could be anything from the boiler locking out only in cold temperatures, through to banging noises in the unit itself.
Can I fix the F68 fault without a gas engineer?
Working on a gas appliance is a job for qualified professionals.
This is even more important if you are a landlord of a rental property. It’s illegal to work on a gas appliance without the proper accreditation (Gas Safe registration).
How will the gas engineer know if low inlet gas pressure is the problem?
A series of tests can be run to determine the pressure of inlet gas.
The first point of call in colder months of the year, is to check the gas meter.
Some properties will have a gas meter fitted outside. This is fine, if they are protected by lagging to insulate them.
However, a lot of gas meters aren’t protected. In cold months, the regulators on the gas meters are prone to freezing.
The fluctuation in flame signal could be due to this freeze over; it gets stronger and weaker as the temperature rises/falls.
What if the meter is supplying gas at the right pressure?
After checking the pressure into the meter is correct, they can check the gas pressure leaving the meter, and to the boiler.
If there’s a problem at the boiler, there could be a few explanations:
- Pipework that’s blocked with debris and restricting the flow of gas
- Incorrect gas valve adjustment, or a faulty gas valve
What can we do if the problem causing the F68 fault code lies with the gas valve?
The problem here is usually limited to incorrect adjustment, or a gas valve fault
Your gas engineer will be able to test the gas valve. If the component is operational, they’ll be able to adjust it, so the flow of gas is correct.
That means you’ll get a steady flow of gas and the boiler’s flame signal won’t fluctuate.
Unfortunately, older boilers are prone to have gas valve failures.
What happens if the gas valve fails?
They’ll not work in symphony with other parts of the boiler.
Once you demand for heat, the gas valve needs to open. The PCB will tell it to open and close when the boiler gets to temperature (close), or needs more fuel (open).
If the gas valve is faulty it could:
- Get stuck in either the open/close position
- Only open/close partially, causing a weak flame and intermittent signal
- Receive intermittent signals, so it doesn’t open and close when it should
- Give out signals that it’s open or closed, when it’s not
Unfortunately, it’s rare that old faulty gas valves can or are worth being fixed.
The gas valve will need to be replaced.
How much does it cost to fit a gas valve, and how long will it take?
Depending on the exact model of your Vaillant, the price for parts will vary. The same goes for labour costs throughout various parts of the country.
However, you should expect to pay around £300 including parts and labour.
The job, including a diagnostic, picking up parts and installation, could take up to a day.
What issues can arise with the flue on my Vaillant boiler?
Flue blockages (the large white tube expelling gases from your property), are very uncommon.
It’s more common for particularly old flues to break apart, than get blocked. But, there’s always the chance of small bits of debris and leaves blowing into the flue.
What’s more common, is a blockage for those using a vertical flue (this will come straight out of your roof).
As it’s easier for debris to make its way into the flue by dropping downwards, than blowing sideways (into a horizontal flue), they should be fitted with a guard.
Different manufacturers produce a range of flue guards and cages. But, if you don’t have one fitted, there’s a good chance it’s debris in your flue causing the issue.
How can a blockage in a flue cause the Vaillant F68 fault code to be displayed?
Flue gas pressure is monitored by the boiler’s internal sensors. For a flue to expel gases correctly, the fan needs to be running, and the flue clear.
When this isn’t the case a sensor tells the boiler it’s not safe to operate and the boiler will lockout.
If this is just a small piece of debris, the air pressure could be fluctuating between a safe and unsafe operating pressure, hence the fluctuating flame signal.
How would the burner contribute to the F68 fault code being displayed?
The burner is what provides heat in the boiler.
As it’s burning gas (or potentially oil/LPG depending on your boiler), it’s going to get carbon build-up over time.
This can make the burner inefficient. But, it can build-up in such quantities that the flame struggles to burn strong.
What’s more common than overall build-up, is bits of carbon finding their way into the jets.
These jets are tiny. A small particle of carbon could partially or fully block the burner and mean it won’t operate correctly.
What’s the fix for a burner that’s not running correctly?
Luckily, most boilers won’t need a new burner. Which is good news considering they can cost around £300 to replace.
Instead of a replacement, your engineer will inspect the burner, clean it, and clean out the jets too.
If this is the only fault, cleaning the burner and a reset, will clear the F68 fault code on your Vaillant boiler.
What can cause the electrode, ignition lead or spark generator to cause the F68 fault?
As the F68 fault relates to a fluctuation in flame signal, it’s rare any of these parts are the core issue.
These parts help to create the initial flame, rather than maintain it.
However, like many other boiler parts, they can get blocked with debris or degrade over time.
Due to the fact they cost little to replace (in comparison to other boiler parts), replacement rather than repair is always the best option.
What else can lead to a F68 fault on my Vaillant boiler?
Vaillant mentions core operational parts as being the most likely culprits. This includes things such as the burner and flue we’ve mentioned above.
But, electrical issues can also cause a fluctuation in flame signal.
When it’s thought electrical issues are causing the flame fault, the first point of call is checking the flame sensor. After all, if the flame sensor isn’t working, it won’t monitor the flame correctly, and the signals it feeds back to the PCB will be incorrect.
Likewise, the PCB can be at fault. In most cases, if the PCB is receiving or giving out the wrong signals due to a fault, it’s likely you’ll have noticed other symptoms.
The most widespread problem that stems from a faulty PCB, is intermittent boiler operation. A typical example would be a boiler that constantly cycles on and off for no reason.
Can an engineer check to see if the PCB is at fault?
It’s likely they’ll check other components first, but the PCB can be inspected.
A visual check will highlight any degraded or damaged wiring, as well as cracks in the main board. Then, further checks using a multi-meter will ensure the PCB is fully operational.
Other Vaillant Fault Codes And Error
If your looking for the list of error codes relating to the Vaillant boiler then please read the article Vaillant Boiler Fault Codes And Cures