Viessmann Vitorond 100 Fault codes & diagnostics

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

Regular Oil 18-107 kW Discontinued

Replaced by: Vitorond 200

The fault code is already on your display

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

Severity at a glance

Each cell = one fault code. Hover to identify.
16 High 3 Medium 5 Low
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 24 documented codes

Tap any card for details

0A

Your boiler's burner has encountered a problem during operation and has shut down as a safety precaution, leaving you without heating and hot water.

High DIY-safe £120-350

What to check first

  1. Locate the reset button on the burner control unit
  2. Press and hold the reset button for at least two seconds
  3. Check that the oil tank has sufficient fuel and that the supply valves are open

Parts commonly replaced

  • Oil nozzle
  • Photoelectric cell (Flame sensor)
  • Ignition electrodes
  • Oil pump
Full explanation for 0A
0D

Your boiler's burner has repeatedly failed to light or stay lit, causing the system to shut down for safety.

High DIY-safe £120-350

What to check first

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

Parts commonly replaced

  • Oil nozzle
  • Photocell (Flame sensor)
  • Ignition electrodes
  • Oil pump
Full explanation for 0D
1A, 1B

Your boiler's burner has stopped working and is locked out, meaning the system cannot fire up to provide heating or hot water.

High DIY-safe £120-280

What to check first

  1. Locate the reset button on the control panel
  2. Press and hold the reset button for at least 2 seconds
  3. Check if the oil tank has run dry and requires a delivery

Parts commonly replaced

  • Oil nozzle
  • Fuel pump
  • Photocell
  • Ignition electrodes
Full explanation for 1A, 1B
1F

Your boiler's oil burner has stopped working and is preventing the system from firing up to provide heat or hot water.

High DIY-safe £120-350

What to check first

  1. Check that your oil tank has sufficient fuel
  2. Ensure the oil supply valve is fully open
  3. Press the manual reset button on the burner control unit once

Parts commonly replaced

  • Oil nozzle
  • Photocell (Flame sensor)
  • Oil pump
  • Ignition electrodes

Related codes

Full explanation for 1F
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
04, 05, 06, 08

Your boiler's burner has repeatedly failed to light or stay lit, causing the system to automatically shut down for safety.

High DIY-safe £120-350

What to check first

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

Parts commonly replaced

  • Oil nozzle
  • Photocell (Flame sensor)
  • Oil pump
  • Ignition electrodes
Full explanation for 04, 05, 06, 08
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
25

Your boiler is getting too hot and has shut itself down to prevent damage to the system.

High DIY-safe £120-350

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the system pressure is between 1.0 and 1.5 bar
  3. Check if the central heating pump is making unusual noises or feels excessively hot

Parts commonly replaced

  • Circulation Pump
  • Boiler Water Temperature Sensor (NTC)
  • High Limit Thermostat
Full explanation for 25
26

Your boiler is stuck in a self-diagnostic 'test mode' and is failing to return to its normal heating cycle.

High DIY-safe £100-£350

What to check first

  1. Locate the main control knob or interface
  2. Turn the boiler off at the main switch for 30 seconds
  3. Switch the boiler back on and wait for the system to reinitialise
  4. If the code persists, ensure no test switches or dials are left in the 'Test' position

Parts commonly replaced

  • Control PCB (Printed Circuit Board)
  • Relay Module
Full explanation for 26
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
Showing 11–20 of 24
222-F

Your boiler has temporarily stopped because it detected air in the system and is now running an automatic process to clear it out.

Medium DIY-safe £0-120

What to check first

  1. Wait for the automatic venting program to finish (this can take up to 20 minutes)
  2. Check that your system water pressure is between 1.0 and 1.5 bar
  3. Ensure all radiator valves are fully open to help air circulate out

Parts commonly replaced

  • Automatic air vent
  • Pressure relief valve
Full explanation for 222-F
A2

Your boiler's burner has encountered a problem and has locked itself out to prevent damage.

High DIY-safe £120-350

What to check first

  1. Press the reset button on the control panel
  2. Check that your fuel supply (oil tank) has enough fuel
  3. Ensure any external shut-off valves are fully open

Parts commonly replaced

  • Oil nozzle
  • Photocell
  • Ignition electrodes
  • Fuel pump
Full explanation for A2
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
All Boilers

Your boiler's main control unit has encountered a programming or setting error that is preventing it from managing your heating and hot water correctly.

High Engineer only £180-650

Parts commonly replaced

  • EVC Control Unit
  • Coding Plug
  • Control Circuit Board
Full explanation for All Boilers
Viessmann boilers

Your boiler is operating normally under its standard settings and there is likely no actual fault to worry about.

Low DIY-safe

What to check first

  1. Check your thermostat to ensure it is calling for heat
  2. Monitor the display to see if the message changes as the house warms up
  3. Consult the user manual to confirm if a specific timer or mode has been accidentally selected
Full explanation for Viessmann boilers
Vitocrossal 200

Your boiler has detected a critical internal error or a mismatch with its electronic settings, causing it to shut down completely for safety.

High Engineer only £180-450

Parts commonly replaced

  • Burner control unit
  • Coding card
  • Ignition electrodes
Full explanation for Vitocrossal 200
Vitocrossal 300

Your boiler is continuing to provide heating but is unable to monitor the exact temperature of the water returning from your system, which may lead to reduced efficiency.

Low Engineer only £140-£260

Parts commonly replaced

  • Low-loss header temperature sensor
  • NTC thermistor sensor
  • Wiring harness connection
Full explanation for Vitocrossal 300
Vitodens 100-W

Your boiler has stopped working because the burner is unable to light or stay lit, meaning your heating and hot water will be unavailable.

High Engineer only £150-450

Parts commonly replaced

  • Ignition electrodes
  • Ionisation lead
  • Gas valve
  • Burner gasket
Full explanation for Vitodens 100-W
Vitodens 200

Your boiler has shut itself down for safety because the internal fan is not spinning at the correct speed to clear out gases.

High Engineer only £250-£550

Parts commonly replaced

  • Fan assembly
  • Burner control unit (PCB)
  • Wiring harness
Full explanation for Vitodens 200
Vitodens 200-W

Your boiler is struggling to monitor water temperature correctly because of a communication issue with a specific sensor, meaning it may not run as efficiently as it should.

Medium Engineer only £120-240

Parts commonly replaced

  • Low-loss header temperature sensor
  • Flow temperature sensor
  • Connection wiring
Full explanation for Vitodens 200-W
Showing 21–24 of 24
Vitodens 222-F

Your boiler's internal control system has encountered a communication error or is set to an incorrect operating mode, preventing it from managing your heating correctly.

Medium DIY-safe £100-250

What to check first

  1. Turn the boiler's power switch off at the wall for 30 seconds and turn it back on.
  2. Access the control menu and ensure the boiler is set to its standard heating and hot water mode.
  3. Check for any external thermostat or smart control connection issues.

Parts commonly replaced

  • External sensor
  • Control PCB
  • Communication module
Full explanation for Vitodens 222-F
Vitotronic 050/200-H

Your boiler has switched on its frost protection mode because the outside temperature has dropped to freezing, which prevents your pipes from icing up.

Low DIY-safe

What to check first

  1. Check that your outdoor sensor is not covered by snow or debris
  2. Ensure your thermostat is set to a comfortable temperature to keep the system active
  3. Monitor the system to ensure it returns to normal operation once the outdoor temperature rises
Full explanation for Vitotronic 050/200-H
Vitotronic 300

Your heating system has switched to a special winter operating mode because it has detected freezing temperatures outside.

Low DIY-safe

What to check first

  1. Check that the outdoor temperature sensor is not covered by snow or ice
  2. Monitor the heating display to ensure the radiators are warming up as expected
  3. Verify that the 'Frost Protection' setting on the Vitotronic control unit is set to your preferred comfort level
Full explanation for Vitotronic 300