Viessmann error codes and what they mean · Hungary
All 3 Viessmann fault codes in one table: what each one means, how serious it is and when to call a pro.
| Code | Appliance | What it means |
|---|---|---|
| F2 | gas boiler | The boiler has overheated and the safety thermostat has shut it down. |
| F4 | gas boiler | The boiler failed to ignite (no flame was detected) and has locked out for safety. |
| F9 | gas boiler | The fan is faulty or is not reaching the correct speed. |