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Understanding fault codes: Quick identification and step-by-step instructions

Vaillant fault codes guide you through any service need for our heat pumps and boilers. Decoding them is simple. Here, you'll learn how to make efficient use of Vaillant's digital code finder for fast and accurate troubleshooting.

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Professional checking system control data log.

Four advantages of using our error code finder

Quick identification

Get the full code description by choosing the product and typing in the code displayed in your customer's app or appliance interface.

Quicker resolution time

Save time by following the diagnostics and instructions provided for each fault code.

Paperless service

No need to browse our hardcopy manuals. Diagnostics, documentation and spare part catalogue are fully integrated in app and desktop application myVAILLANT Pro Service.

Enhanced information

See full list of status, maintenance and fault codes of a system in online diagnostics.

Resolve your customer's fault code smoothly

Get started with online diagnostics in myVAILLANT Pro Service now.
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Crack the code: Vaillant fault codes explained

Vaillant appliances have five types of notifications. Spotting the differences is easy. Reading them on our systems? Just as simple. Here are your options:

F-Code

Fault code.

An ecoTEC plus boiler in a utility room

F-codes signal a malfunction that locks the device. Immediate expert intervention is required. Notifications about an F-code are delivered through these interfaces:

  • myVAILLANT app
  • HVAC appliance interface
  • Remote System Monitoring (if appliance is managed in myVAILLANT Pro Service)

N-Code

Limp home mode irreversible.

Woman folding towels in a utility room with a ecoTEC plus boiler in the background

N-codes indicate a functional limitation that only an expert can resolve. The device switches to Comfort Safety Mode. N-codes can be accessed through the following interfaces:

  • HVAC appliance interface
  • Remote System Monitorung (if appliance is managed in myVAILLANT Pro Service)

L-Code

Limp home mode reversible.

Man carrying a washing basket walking through a utility room with a ecoTEC plus boiler in the background

L-codes indicate a temporary functional limitation that will be resolved automatically. The HVAC appliances switches to Comfort Safety Mode until full functionality is restored. L-codes can be accessed via the following interfaces:

  • HVAC installer level
  • Remote System Monitoring (if appliance is managed in myVAILLANT Pro Service)

I-Codes (former M-Code)

Maintenance Code.

A woman carrying a laundry basket through a utility room. There is a boiler on the wall in the background.

I-codes alert you to upcoming maintenance needs to ensure smooth operation. The device simultaneously notifies both owners and operators when an I-code occurs.

  • myVAILLANT app
  • HVAC appliance interface
  • Control display
  • Remote System Monitoring (if appliance is managed in myVAILLANT Pro Service)

S-Code

Status Code.

A side view of a boiler on the wall. There is a briefcase on the worktop with the Vaillant logo.

S-codes provide information on which defined states are active in the HVAC system, with no immediate action required. They are purely informative and helpful for troubleshooting. The device stores the last ten status messages. Through myVAILLANT Pro Service Status, you gain access to an extended status history.

  • HVAC installer level
  • Remote Sytem Monitoring (if appliance is managed in myVAILLANT Pro Service)

Ready to have all HVAC notifications at your fingertips?

Add your Vaillant installations to myVaillant Pro Service app now and go digital with system monitoring!
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From fault code to solution in three simple steps

The myVaillant Pro Service tool contains all the functions, from identifying the fault type to successful troubleshooting.

The Code Finder is also available to you even without registered systems. For extended functionality, please register your Vaillant installations and activate guided service.
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1

Access and read fault code

View the device log when you are at your customer's property or receive a notification directly to your inbox when the device is managed in myVaillant Pro Service.
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2

Get description and diagnostics

Each error code is listed with a description and ad-hoc analysis in the manual. For a quicker solution, use the online Code Finder. Note: ecoTEC plus and ecoTEC exclusive generate status QR code for scan in installer level.
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3

Plan spare parts and intervention

Get the right part quickly and reliably with myVaillant Pro Service or the spareCHECK app. For complex tasks, unlock the step-by-step guide as an additional resource.

What's the problem?

Frequent heat pump fault codes and possible root causes.

Getting your customer's heating system back on track

Frequent boiler fault codes and how to solve them.

Grow your expertise and facilitate your work

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Deepen your knowledge with our training courses

Everything you need to know about our heating appliances – acquire new skills either remote or in-centre with our experts.
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myVAILLANT Pro Service

myVAILLANT Pro Service: Now featuring spare parts catalogue.

Unlock the power of myVAILLANT Pro Service. Check fault codes and order spart parts all in one step.
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