Viessmann Vitopend 100 Fault codes & diagnostics

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

Combi Natural Gas 24-30 kW 1994-2010 Discontinued

Replaced by: Vitodens 100-W

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 8 Low
Just want the most common Viessmann Vitopend 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 has detected an issue with the gas supply pressure and has shut down as a safety precaution.

High DIY-safe £100-280

What to check first

  1. Check if other gas appliances, like a gas hob, are working correctly to confirm fuel supply.
  2. Ensure the gas stopcock valve is fully open at your gas meter.
  3. Press the 'Reset' button or turn the control dial to 'Reset' once and wait for the boiler to restart.

Parts commonly replaced

  • Gas pressure switch
  • Gas valve
  • Ignition electrodes
Full explanation for 0A
0D

Your boiler has detected a communication or ignition fault and has shut down as a safety precaution to prevent damage.

High DIY-safe £180-450

What to check first

  1. Locate the reset button or dial on the front control panel
  2. Press or turn to 'Reset' for several seconds and release
  3. Wait for the boiler to attempt to restart; if the code returns immediately, contact a gas safe engineer

Parts commonly replaced

  • Ignition Electrode
  • Gas Valve
  • Printed Circuit Board (PCB)
Full explanation for 0D
1A, 1B

Your boiler has shut down because the burner cannot fire correctly, often due to a lack of gas or a restricted air supply.

High Engineer only £120-350

Parts commonly replaced

  • Ionisation electrode
  • Ignition unit
  • Gas valve
Full explanation for 1A, 1B
1F

Your boiler's burner has shut down because it is struggling to maintain a stable flame or has become fouled, leaving you without heating and hot water.

High Engineer only £120-350

Parts commonly replaced

  • Burner assembly
  • Ignition electrode
  • Ionisation probe
  • Heat exchanger
Full explanation for 1F
02

Your boiler has shut down because it has detected an overheating issue and has locked itself for safety.

High DIY-safe £100-£350

What to check first

  1. Check that your home's radiator valves are open and not turned to the lowest setting.
  2. Ensure there is enough pressure in the system by checking the digital or needle gauge.
  3. Press the Reset button on the boiler control panel to see if the fault clears.

Parts commonly replaced

  • Circulation pump
  • Overheat thermostat
  • Temperature sensors (NTC)
Full explanation for 02
04, 05, 06, 08

Your boiler has detected a safety problem with the flame or internal electronics and has shut itself down to prevent damage.

High Engineer only £120-350

Parts commonly replaced

  • Burner control unit
  • Ignition electrodes
  • Flame sensing electrode
Full explanation for 04, 05, 06, 08
07, 09

Your boiler has detected a communication or electrical fault with the burner control unit and has shut itself down for safety.

High Engineer only £180-450

Parts commonly replaced

  • Burner Control Unit
  • Printed Circuit Board (PCB)
  • Wiring Harness
Full explanation for 07, 09
25

Your boiler is getting too hot too quickly, which is usually caused by water not flowing through the system properly.

High DIY-safe £120-350

What to check first

  1. Check that all radiator valves are fully open
  2. Ensure the boiler pressure is between 1.0 and 1.5 bar
  3. Bleed your radiators to remove any trapped air

Parts commonly replaced

  • Circulation pump
  • Temperature sensors (NTC)
  • Main heat exchanger
Full explanation for 25
26

Your boiler is stuck in a self-diagnostic test mode and is unable to move into its normal heating cycle.

High DIY-safe £120-350

What to check first

  1. Turn the boiler power switch to 'OFF' for 30 seconds
  2. Turn the power switch back to 'ON'
  3. If the code persists, turn the main mode selector dial to 'Reset' for 3 seconds and release

Parts commonly replaced

  • Printed Circuit Board (PCB)
  • Relay module
Full explanation for 26
35

Your boiler has failed to ignite and cannot provide heating or hot water, likely because it hasn't detected a flame after several attempts.

High Engineer only £120-300

Parts commonly replaced

  • Ignition electrodes
  • Gas valve
  • Ionisation lead
  • PCB
Full explanation for 35
Showing 11–20 of 24
222-F

Your boiler has detected trapped air inside the system and is currently trying to clear it out to prevent the burner from overheating.

Low DIY-safe £0-120

What to check first

  1. Wait for the boiler to complete its automatic 20-minute venting cycle
  2. Check that your radiator valves are open
  3. Check the boiler pressure gauge and top it up to 1.5 bar if it is too low

Parts commonly replaced

  • Automatic air vent
  • Circulation pump
Full explanation for 222-F
A2

Your boiler has stopped working because the fan is unable to clear air from the combustion chamber properly.

High Engineer only £180-350

Parts commonly replaced

  • Fan assembly
  • Air pressure switch
  • Main PCB
Full explanation for A2
A5

Your boiler has detected that the internal pump is stuck or there is very little water pressure, preventing it from heating your home.

High DIY-safe £180-350

What to check first

  1. Check the pressure gauge and top it up to 1.5 bar using the filling loop
  2. Ensure all radiator valves and isolation valves are fully open
  3. Restart the boiler to see if the pump clears itself

Parts commonly replaced

  • Circulation pump
  • Pressure sensor
  • Expansion vessel
Full explanation for A5
All Boilers

Your boiler's computer is struggling to communicate with its internal sensors or external controls, meaning it cannot decide how much heat to produce.

High Engineer only £180-450

Parts commonly replaced

  • Main PCB (Control Board)
  • Communication Module
  • External Thermostat
Full explanation for All Boilers
Viessmann boilers

Your boiler is currently operating based on internal settings rather than external controls, meaning it may be ignoring your thermostat or running according to the temperature set on the boiler panel itself.

Low DIY-safe £0-120

What to check first

  1. Check that your room thermostat is turned up and has working batteries
  2. Ensure the heating and hot water dials on the boiler front panel are set to your desired temperature
  3. Check if any external timers or smart controls are disconnected or powered off

Parts commonly replaced

  • Room thermostat
  • External programmer
  • Control PCB
Full explanation for Viessmann boilers
Vitocrossal 200

Your boiler has shut down and locked itself for safety because the electronic control unit has detected a serious internal communication error or an incorrect setup component.

High Engineer only £180-450

Parts commonly replaced

  • Burner Control Unit
  • Coding Card
  • Ignition Electrode
Full explanation for Vitocrossal 200
Vitocrossal 300

Your boiler is continuing to work but cannot accurately measure the water temperature in a specific part of your system, usually because a sensor is missing or disconnected.

Low Engineer only £90-180

Parts commonly replaced

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

Your boiler has failed to ignite the flame after several attempts and has shut down as a safety precaution.

High Engineer only £120-450

Parts commonly replaced

  • Ignition electrode
  • Gas valve
  • Condensate trap
  • Printed Circuit Board (PCB)
Full explanation for Vitodens 100-W
Vitodens 200

Your boiler has shut itself down because the internal fan is not spinning at the correct speed to safely clear out exhaust fumes.

High Engineer only £250-£550

Parts commonly replaced

  • Extraction fan
  • Fan wiring harness
  • Burner control unit (PCB)
Full explanation for Vitodens 200
Vitodens 200-W

Your boiler is still providing heat, but it has lost communication with a specific temperature sensor that helps it run at maximum efficiency.

Low Engineer only £120-220

Parts commonly replaced

  • Flow temperature sensor
  • NTC thermistor
  • Wiring harness
Full explanation for Vitodens 200-W
Showing 21–24 of 24
Vitodens 222-F

Your boiler is currently operating in a basic manual backup mode because it has lost communication with its external controls or sensors.

Low DIY-safe £0-120

What to check first

  1. Check if the batteries in your room thermostat need replacing
  2. Ensure the boiler's control dials are set to the correct positions for your heating schedule
  3. Perform a simple reset by turning the power off and back on again

Parts commonly replaced

  • Room thermostat batteries
  • Outdoor temperature sensor
  • Internal communication cable
Full explanation for Vitodens 222-F
Vitotronic 050/200-H

Your heating system has switched to frost protection mode because the outside temperature has dropped to freezing, ensuring your pipes do not freeze.

Low DIY-safe

What to check first

  1. Check that your outdoor temperature sensor is not covered by snow or debris
  2. Ensure your heating settings are adjusted to your comfort level for cold weather
  3. Monitor the system to ensure it returns to normal operation when the temperature rises
Full explanation for Vitotronic 050/200-H
Vitotronic 300

Your boiler's outdoor temperature sensor has detected freezing conditions and is telling your heating system to run continuously to prevent your pipes from freezing.

Low DIY-safe £0-60

What to check first

  1. Check that the outdoor sensor is not covered by snow or ice
  2. Monitor the heating system to ensure radiators are getting warm as expected
  3. No action is typically required as this is an automatic frost protection feature

Parts commonly replaced

  • Outdoor temperature sensor
  • Sensor wiring
Full explanation for Vitotronic 300