Viessmann Vitorond 100 Fault codes & diagnostics

5 fault codes with plain-English explanations, severity ratings, DIY guidance, and repair cost estimates.

Regular Oil 18-107 kW Discontinued

Replaced by: Vitorond 200

Download the Viessmann Vitorond 100 manual The official installation & service manual (PDF) — the exact document these fault codes were verified against. PDF

The fault code is already on your display

Note it down before pressing reset — resetting clears the code immediately. How to read fault codes →

Just want the most common Viessmann Vitorond 100 faults?
The top 6 problems in plain English — with causes, DIY checks and repair costs.
Fault codes

All 5 documented codes

Tap any card for details

02

Your boiler's burner has shut itself down for safety because it failed to light or maintain a flame.

High DIY-safe £100-£350

What to check first

  1. Check that you have fuel in your oil tank
  2. Ensure the oil supply valves are fully open
  3. Press the illuminated reset button on the burner control unit once

Parts commonly replaced

  • Oil nozzle
  • Fuel filter
  • Photocell (flame sensor)
  • Oil pump
Full explanation for 02
07, 09

Your boiler has detected a problem with the burner and has shut itself down as a safety precaution, meaning you will not have any heating or hot water.

High DIY-safe £120-450

What to check first

  1. Check that you have not run out of heating oil in your storage tank
  2. Ensure the oil shut-off valve is fully open
  3. Press the reset button on the burner control unit once to see if the boiler restarts

Parts commonly replaced

  • Oil nozzle
  • Photocell / Flame sensor
  • Oil pump
  • Ignition electrodes
Full explanation for 07, 09
35

Your boiler is failing to start up when it is supposed to be heating your home.

High DIY-safe £120-280

What to check first

  1. Check if your fuel tank has enough oil
  2. Press the reset button on the burner controller once
  3. Ensure the external oil supply valve is fully open

Parts commonly replaced

  • Oil Burner Control Unit
  • Photocell (Flame Sensor)
  • Oil Pump
Full explanation for 35
A5

Your boiler has stopped heating because it has detected a problem with the internal pump or water circulation.

High DIY-safe £180-450

What to check first

  1. Check that your home's radiator valves are fully open
  2. Inspect the boiler pressure gauge and ensure it is between 1.0 and 1.5 bar
  3. Press the reset button on the control panel once

Parts commonly replaced

  • Circulation pump
  • Flow temperature sensor
  • Heat exchanger
Full explanation for A5
b7

Your boiler's internal computer is missing a specific identification card needed to recognize how your heating system is configured, causing it to stop working for safety reasons.

High Engineer only £150-300

Parts commonly replaced

  • Coding card
  • Boiler control unit

Related codes

Full explanation for b7
Status & diagnostic codes

3 operating states & engineer diagnostics

Not faults — these are normal operating states. Tap to expand.

25 Status Your boiler is getting too hot and has shut itself down to prevent damage to the system. 26 Diagnostic Your boiler is stuck in a self-diagnostic 'test mode' and is failing to return to its normal heating cycle. Viessmann boilers Status Your boiler is operating normally under its standard settings and there is likely no actual fault to worry about.