Viessmann fault & error codes

If your Viessmann boiler has stopped working, it can be frustrating, especially if it leaves you without hot water or central heating. To give you an idea of what the problem is, however, an error code will likely be displayed on your boiler’s interface. 

Viessman boiler fault codes are designed to ensure problems can be diagnosed more quickly, meaning boiler technicians can get your system back up and running more quickly. 

To further reduce the time you’re left without a functioning boiler, we put this handy guide together so you’re not left wondering what’s wrong for too long. 

Viessmann fault & error codes by code

• Fault code 5C, 5D, 5E and 5F
• Fault code 10
• Fault codes F6, 58, F9, F-E1, F-E2 and F-F6
• Fault codes 18 and D1
• Fault code A4
• Fault code OC

How to reset a Viessmann boiler

The way to reset your boiler will vary depending on your Viessman boiler. You may need to turn a dial or press a series of buttons. Make sure to check your boiler’s manual for specific instructions relating to your system. 

Before resetting your boiler, you must check which fault code is displayed to determine whether you can fix the problem. For example, if your boiler has locked you out because the pressure is too low, this is something you can remedy yourself. You must not attempt difficult or complex repairs, though. Anything requiring more than a simple fix must be repaired by a qualified Gas Safe registered engineer. 

How to increase pressure on a Viessmann boiler

Most Viessman boilers have an operating pressure of 1-1.5 bar. This is usually shown as a green zone on the pressure gauge. 

On Viessmann system and combi boilers, the pressure gauge can be found in the control panel. Meanwhile, for standard (regular or heat-only) boilers, the pressure gauge is fitted in the pipework just below the boiler. 

Before increasing the pressure on your boiler, you should consult the boiler’s instructions for specific guidance and ensure you feel comfortable repressurising the boiler yourself. If you are in any doubt about what to do, always contact a Gas Safe registered engineer for help.

If you feel confident in repressurising your boiler, follow the instructions below.

1. Locate the filling loop and pressure gauge - filling loop handles should be at a 90o angle to the flow direction of the pipe.
2. Make sure you can see the pressure gauge once you find the filling loop. This will help you ensure you’re not over- or under-filling the pressure gauge.
3. The correct pressure level will be shown in green.
4. Turn the boiler off.
5. Turn the filling loop handles so they match the direction of the pipe. You should hear water flowing when you do this.
6. Remember to keep an eye on the pressure gauge so you don’t add too much pressure. Once you’ve reached the green spot, usually between 1-1.5 bar, make sure the handles are fully closed by returning them to their original position.
7. Turn the boiler back on and check the pressure remains consistent. If the pressure remains steady, the issue will likely be resolved. If not you should contact a Gas Safe registered engineer to investigate further. 

Viessmann boiler error codes

Here are some of the most common Viessmann error and fault codes, and what they mean.

Fault codes 5C, 5D, 5E and 5F

Boiler mode	Problem
Vitotronic 300-K with Vitotronic 200 control	The system has gone into control mode due to a communication fault.

Fault code 10

Boiler mode	Problem
Vitodens 200-W / 222-F / Vitotronic 300 / 200/ 200-H / 050/200-H / 300-K / vitocontrol-S	The outdoor temperature sensor has short-circuited - the boiler is operating as though the outdoor temperature is 32°F / 0°C.
Vitotronic 300-K, MW2S with Vitotronic 100 / Vitodens 100-W (combiPLUS) / 200-w / Vitocontrol-S, WB2B with Vitotronic 100	The outdoor temperature sensor has short-circuited - the boiler is operating as though the outdoor temperature is 32°F / 0°C.

Fault codes F6, 58, F9, F-E1, F-E2 and F-F6

Boiler mode	Problem
All Viessman boilers	The burner is in fault/emergency operation mode.

Fault codes 18 and D1

Boiler mode	Problem
Vitodens 100 / 200-W / 222-F / Vitotronic 300-K With 100 / Vitocontrol-S	The outdoor temperature sensor is broken - the boiler is operating as though the outdoor temperature is 32°F / 0°C.
Vitotronic / 100 / 200 / 300 / 050/200-H /300-K / Vitocontrol-S, MW1 with Vitotronic 100	A circuit on the outdoor temperature sensor is open - the boiler is operating as though the outdoor temperature is 32°F / 0°C.
Vitotronic 200-H / Vitotronic 300-K, MW1B with Vitotronic 300 / Vitotronic 300-K, MW2B with Vitotronic 200	The outdoor temperature sensor is broken due to a lead break - the boiler is operating as though the outdoor temperature is 32°F / 0°C.
Vitotronic 050/200-H	The outdoor temperature sensor is broken - the boiler is operating as though the outdoor temperature is 32°F / 0°C.
Vitodens 100-W	The burner is in fault mode, and DIP switch S2 is turned on.

Fault code A4

Boiler mode	Problem
Vitodens 222 F	The burner is blocked, and the venting program is started automatically - caused by an airlock in the internal circulation pump or the minimum flow rate not being achieved.

Fault code OC 

Boiler mode	Problem
Vitodens 100-W	The burner is blocked due to an insufficient power supply.
Vitodens 200	The burner control has switched to lockout due to the flame signal still being present after switching off.