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Vaillant Boiler F68 Fault Code

The Vaillant fault code F70 boiler softwear problem Q & A or require an engineer for an emergency boiler repair.


The Vaillant Boiler Fault Code F70 Error Common Q&A

Vaillant Boiler F70 Fault Code

Vaillant Boiler F70 Fault Code Error
  • What does the F70 fault code mean on my Vaillant boiler?
  • What causes the F70 fault code to be displayed?
  • What does the PCB in my Vaillant boiler do?
  • Should I get the manufacturer to fix the PCB fault?
  • How will I know if the PCB is broken?
  • What will the engineer do to diagnose a faulty PCB?
  • If I have a leak, what should I do?
  • Can the PCB be fixed, to clear the F70 fault code?
  • What is the user interface on my Vaillant boiler, and how can that cause the F70 fault?
  • If the user interface is the issue, what can be done to clear the F70 fault code?
  • How would a replacement PCB and bad setup, cause the F70 fault code to be displayed?

What does the F70 fault code mean on my Vaillant boiler?

According to Vaillant’s error code guide, the F70 fault code relates to a software problem.

The actual description is “incompatible software”.

When your boiler doesn’t recognise the software, the main PCB (printed circuit board) can’t communicate with other boiler parts. So, the boiler won’t be operational.

What causes the F70 fault code to be displayed?

The incompatible software fault can occur when:

  • The PCB is faulty
  • The user interface on the PCB is faulty
  • A new PCB has been fitted, and has not been correctly setup by the engineer

What does the PCB in my Vaillant boiler do?

The PCB is the heart of any boiler. It sends and receives signals to and from important parts.

This tells parts on the boiler to run, stop, open and close.

This includes parts such as:

  • The fan, to push harmful gases into the flue
  • The gas valve, to provide fuel to the burner
  • The pump, to circulate water around your heating system

But, it also sends and receives signals to sensors that ensure the boiler is operating in conditions that are safe, such as:

  • Water pressure sensors
  • Flame signals
  • Air pressure sensors

Without being able to interact with these parts (due to a software problem), the boiler will lockout and display the F70 fault code.

Should I get the manufacturer to fix the PCB fault?

If the problem is diagnosed as being a faulty PCB, or interface problem, this should be good news.

Manufacturers should cover the PCB under their warranty. It’s not a consumable part that breaks easily, or quickly.

How will I know if the PCB is broken?

To make the job as quick as possible for the engineer (and therefore, lower labour costs), it’s worth noting all the issues you’ve noticed with your boiler recently.

Up until the boiler locked out and displayed the F70 fault code, it might have:

  • Turned off and on sporadically, even when you’ve not turned the heating on
  • Had a display panel that was flickering
  • Cycled on and off constantly when the heating is on
  • Had a fan that wouldn’t turn off

These are operational faults that are signs of bad signals. This may be PCB related, or it could be bad wiring.

Besides from operational clues, there are some other things you might have noticed, coupled with the above:

  • The boiler was leaking from the casing
  • There was a slight burning smell, that grew stronger over time

What will the engineer do to diagnose a faulty PCB?

The information you provide them is going to help with the diagnostic. Especially when it comes to intermittent boiler operating, given these issues might not show themselves when they arrive.

A boiler’s PCB will break due to:

  • Old age
  • Bad wiring (either aged, or broken)
  • Boiler leaking water, that has found itself onto the PCB
  • A burnt-out circuit board

A visual inspection will be first. This can highlight potential problems such as surface cracks on the PCB. If these hairline cracks pass through soldered joints, it’s likely they are interfering with the signals the PCB gives and receives.

Further inspection will allow the engineer to see the state of the wiring. Damaged or degraded wiring will need to be repaired or replaced.

Finally, they’ll check for burnt out sections of the PCB. This can be caused by water leaks or condensation build-up in the boiler.

If I have a leak, what should I do?

Even when a leak hasn’t led to a PCB failure, it needs to be fixed. This can cause a whole host of problems, and not just property damage.

You’ll start to see various fault codes relating to low pressure, dry fires and even electrical errors.

Make sure the engineer finds and fixes the leak before replacing the PCB. Otherwise, you’ll have spent a lot of cash, only for the same problem to occur.

Can the PCB be fixed, to clear the F70 fault code?

Anything can be fixed, but at what cost? The engineer will need to assess not just the damage, but also the age of the boiler and PCB.

It doesn’t make sense to spend too much time fixing an old and worn out part. A replacement PCB can be fitted for around £350 (depending on the model of your boiler).

At the same time, the engineer needs to consider if a boiler replacement is a more cost-effective option, long-term.

After all, there’s little point investing £350 in an old boiler, when other expensive parts could be on their way out too.

To determine the overall state of the boiler, they’ll need to assess the condition of the:

  • Fan
  • Pump
  • PCB
  • Heat Exchanger
  • Gas Valve

Typically, the result for boilers under 5 years old, is simply to replace the PCB.

What is the user interface on my Vaillant boiler, and how can that cause the F70 fault?

The user interface is the display panel on the front of your boiler.

It may have flashing lights, reset buttons and of course, a small screen which is where the F70 fault code will be displayed.

If the user interface is the issue, what can be done to clear the F70 fault code?

Whereby the F70 fault code relates to the display panel, that’s the boiler telling you that it’s not receiving instructions how it should.

For instance:

  • The temperature dials may be faulty
  • The buttons on your boiler may be faulty
  • The communication between the display panel and the circuit board could be non-existent

In these cases, a replacement panel will clear the F70 fault code and allow the boiler to operate again.

How would a replacement PCB and bad setup, cause the F70 fault code to be displayed?

For most modern boilers, the setup procedure for replacement PCBs is simple. The setup syncs the PCB with the software and boiler. Without these three things in sync, the boiler won’t work.

If the boiler engineer hasn’t inputted product codes correctly, the boiler won’t sync with the software.

This is incredibly rare. A boiler needs to be tested before it’s considered to be Gas Safe and “signed off”. Without the correct PCB setup, the engineer can’t test the boiler.

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