What does F4 mean on a Viessmann boiler?
Andrew Mclaughlin
Updated on March 02, 2026
If you’re seeing the F4 fault code being displayed on your Viessmann boiler, the problem lies with lack of flame detection. When you demand for hot water or heating, your boiler gives the signal to all relevant parts. That includes the likes of the gas valve to open, and the burner to fire up.
How long are Viessmann Boilers guaranteed for?
Many of the boilers come with a comprehensive 5 year parts and labour warranty, as standard. Optional warranty extensions are available if the boiler is installed by a Viessmann Academy Trained Installer.
Is it safe to reset a boiler?
Often, a boiler can be returned to normal working order by resetting it. If your heating isn’t coming on and you’ve checked the power supply and pressure you may need to reset the boiler. It’s a very simple and safe thing for you to do in your own home.
Why is my Viessmann boiler not working?
If you think you’ve fixed the problem but your boiler still keeps shutting down, it’s likely that you have an ongoing fault. This could be something like a broken pump, a leak somewhere in the system, an electrical issue or a blocked heat exchanger.
What boilers have 10 year warranty?
Best 10 Year Warranty Boilers
| Boiler Brand | Warranty (min to max) |
|---|---|
| Viessman | 2 – 10 years |
| Worcester Bosch | 2 – 12 years |
| Ideal | 2 – 12 years |
| Vaillant | 2 – 10 years |
What does intermittent F4 fault mean on a Viessman vitodens 100?
Hi fellas, got an intermittent f4 fault on a viessman vitodens 100. when the fault occurs it has a loud ignition as if the spark isn’t catching the gas first time but then the flame doesn’t stay on, it repeats before locking out. notice their is only one elcectrode on these for sparking and flame rectification. Possible ionisation electrode fault?
What happened to the vitodens 100?
The Vitodens 100 has been redesigned in the last year or so. Apparently the early electronic circuit boards were not reliable and many of them have been replaced under warranty (I have heard the manufacturers acted very fairly).
How long does it take a Viessmann 100 to fail?
Its virtually always the ignition unit. But there is no test you can do apart from replacing it. On the seven Viessmann 100s that I have installed, most have failed within 1-10 weeks. I have been told that very rarely it can be caused by the PCB but I have no firm evidence of ANY which were really the PCB.
What is wrong with my vitoden 100 boiler?
They know first generation Vitodens 100 boilers had some problems. So ring them up and get it sorted. If your system is a gas system either natural or propane. If your system was not set up properly which it sounds like it was not set up properly.
