Viessmann F5 Fault

Viessmann F5 Fault

Generally, when the code F5 is displayed on the Viessmann boiler screen, it means that there is a problem with flame signal. In other words, this means that the boiler has been experiencing multiple flame failures during its operations. This is due to various causes that may affect ignition process or flame stability; therefore, identifying and fixing the root cause of this problem is essential for safe and efficient operations of the boiler.
Reasons Why Boiler Displays F5 Fault Code

Gas Supply Issues: Inconsistent gas pressure or intermittent supply can cause the burner not maintain a steady flame.

Malfunctioning Ignition Electrodes: Ignition electrodes which are worn out, not correctly aligned and dirty cannot ignite gas uniformly thus resulting in flames going off.

Blocked Burner: If your burner is dirty or blocked, it may impede flow of gas leading to unstable flames.

Flame Sensor Problems: A faulty or contaminated flame sensor will fail to detect combustion accurately prompting numerous boiler shut downs.

Air Supply & Flue Problems: Combustion requires sufficient air flow. If there are obstructions/leaks in either air supply or flue system then flame would be disturbed.

F5 Fault Code Troubleshooting and Solutions

Check Gas Supply: Ensure continuous gas supply and its pressure remains within recommended levels. To rectify situations where gas pressure seems inadequate, engage an engineer registered under Gas Safe to assess and regulate pressure.

Review Ignition Components’ Cleanliness: Check for wear, misalignment or dirtiness on ignition electrodes. Reliance on clean burners as well as properly arranged electrodes can however restore normality regarding these bursts of flames.

Clean Your Flame Sensor Carefully: Remove possible deposits from your sensor cautiously; otherwise change a broken one through assistance of experts alone.

Inspect Air Supply & Flue System Check whether there is anything obstructed in flues or air intake that can interfere with burning processes Standard regulation might lead to some professional interventions in this case.

Reset Boiler: In order to delete the fault code and turn it on again, simply reset your boiler once you have rectified any known problems. However, if F5 error repeat itself, then more expert evaluation is needed.

Seek Professional Assessment: If you have been receiving such flame failures as reflected by the F5 code, then contact a Gas Safe engineer who will scrutinize and come up with a detailed report touching on gas valve, control board or any other aspects that may contribute to these challenges.


The Viessmann’s F5 fault code is an indicator of a highly serious problem with flame stability which might compromise the safety and functionability of your heater. But while some basic repairs can be attempted by home-owners, most causes for showing F5 error demand professional diagnosis and fixing so as not to endanger you when using it later. Make sure that your device goes through regular maintenance scheduled by those who are qualified enough in order to avoid everything that could go wrong with it as well as keep the whole unit in its best working conditions.