Viessmann Boiler Fault Codes Explained

There is never a good time for your Viessmann boiler to display a fault code but hopefully this simple guide will restore some peace of mind by running through so of the more common fault codes and what they mean.

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If your Viessmann boiler develops a fault, it will usually go into a safety lockout and display an error code on the control panel. These codes are designed to help identify what’s wrong with the system so that the issue can be diagnosed quickly and safely.

Understanding these fault codes can give you valuable insight into the problem before you call a qualified Gas Safe registered heating engineer, but never attempt to open or repair your boiler yourself, as this can be dangerous and may void your warranty.

At Just Gas, we specialise in diagnosing and repairing Viessmann boilers efficiently across Torquay and the surrounding area.

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What Are Viessmann Boiler Fault Codes?

Viessmann boilers use a system of fault codes, usually beginning with a letter such as  “F” or “BE”, to indicate when something isn’t functioning correctly.

These codes help engineers quickly pinpoint the cause of the fault, making repairs faster and more cost-effective. If you can tell us the displayed fault code when you contact us, we’ll be in a better position to identify the likely issue before attending your property.

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Common Viessmann Boiler Fault Codes

Here are some of the most frequently encountered Viessmann boiler fault codes and what they typically mean:

60, 68, 70, 78, BD, BE, BF – No Output Reduction / Sensor Issue

Cause: G Return control open, max temp reached, or temperature sensor short/open.

Solution: Professional diagnosis needed.

Cause: Lead break, sensor or control unit problem.

Solution: Professional repair needed.

Cause: Internal control error; hardware mismatch.

Solution: Professional diagnostics required.

Cause: Boiler cools down because the fixed high limit has been triggered or fuse F2 has blown.

Solution: Have a qualified Gas Safe engineer inspect the boiler to reset the high limit or replace the blown fuse.

Cause: Boiler reaches the electronic maximum temperature because it is not logging in with the cascade control unit.

Solution: Professional inspection recommended.

Cause: Ionisation current too high; pump, air block or sensor issue.

Solution: Needs qualified engineer investigation.

Cause: Burner has entered error mode because the fan wasn’t at a standstill or there’s a plug-in connection error.

Solution: Engineer to inspect fan and electrical connections.

Cause: Communication fault with the boiler.

Solution: Requires engineer attention.

Cause: PCB fault or strong interference field

Solution: Engineer required.

If you don’t see the fault code from your Viessmann boiler in this list, take a look at the Viessmann website for more information on your specific boiler model.

Should You Fix a Boiler Fault Yourself?

Most Viessmann fault codes point to internal components or gas-related systems, which should only be handled by a qualified professional.

Whilst some simple issues like low pressure can be resolved at home, attempting any complex repairs yourself can be dangerous and could invalidate your manufacturer warranty.

When to Call a Heating Engineer for your Viessmann Boiler

You should contact a professional if:

  • The same fault code keeps reappearing 
  • The boiler won’t reset 
  • There is no heating or hot water 
  • You notice odd noises or smells 
  • You’re unsure what the code means 

Our experienced engineers at Just Gas are fully qualified to diagnose and repair all Viessmann boiler fault codes safely and efficiently.

Viessmann Boiler Repairs in Torquay

We offer:

  • Fast response times
  • Reliable and friendly service
  • Transparent pricing
  • Fully qualified, Gas Safe registered engineers

Whether it’s a straightforward fix or a more complex repair, we’ll work quickly to get your heating and hot water back on.

Viessmann Boiler Fault Code FAQs

If your Viessmann boiler is showing a fault code, you probably have questions. Here are the ones we hear most:

What do Viessmann boiler fault codes mean?

Viessmann boiler fault codes are diagnostic messages that appear when the system detects an issue. Each code corresponds to a specific fault, helping engineers identify problems faster.

This can vary from model to model but, typically, you can reset a Viessmann boiler by turning the heating dial to the reset symbol and then quickly back to the original spot. On some models you press “Mode” and “OK” simultaneously for a few seconds. Please refer to your boiler manual for how to reset your Viessmann boiler model.

This could be caused by a leak, recently bled radiators, or a faulty pressure component. Repeated pressure loss should be checked by a qualified engineer.

Simple issues, such as adjusting pressure can be done at home, but most boiler faults require a Gas Safe registered engineer.

No, if your boiler is showing a fault code, it’s best to switch it off and get it checked. Continuing to use it could cause further damage or safety risks.

No, if your boiler is showing a fault code, it’s best to switch it off and get it checked. Continuing to use it could cause further damage or safety risks.

Repair costs vary based on the fault. Simple fixes may be affordable, while more complex issues involving component replacement will cost more. Contact us for a transparent quote.

Call an engineer if:

  • The fault won’t clear after resetting 
  • Your heating or hot water has stopped working 
  • The same fault keeps coming back 
  • You have any safety concerns 

Yes, Viessmann boilers typically come with manufacturer warranties that vary based on model and installation. Always check your documentation before arranging repairs.

Yes, annual servicing helps keep your boiler running efficiently and can catch issues before they result in fault codes.

Need Help with a Viessmann Boiler Fault Code?

If your boiler is showing an error code and you’re unsure what to do, we’re here to help.

Call: 01803 555577
Email: info@justgasltd.co.uk

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