BoilerFaultCodesThe 6 most common faults
Your boiler's internal fan isn't starting, so it has shut itself down as a safety precaution and will need a qualified engineer to check it.
Full guide for F9Your boiler is trying to light but cannot get the flame started, so it has shut itself down to stay safe, and this usually means you have no heating or hot water until a engineer checks it.
Full guide for EEThe boiler is pausing while it sets up its gas-burning settings, and it needs a reset and a check that water is flowing freely through the heating system before it can run properly again.
Check the pressure gauge on the front of the boiler. It should read between 1 and 1.5 bar when the system is cold. If it is low, top it up using the filling loop as shown in the user manual, then close the filling loop valves.Bleed any radiators that feel cold at the top or are cold all over, using a radiator key, to remove trapped air that can block water flow.Make sure all radiator valves and any isolation valves are fully open so water can circulate freely.Press and hold the reset button marked R on the boiler control panel for a few seconds, then release it. Wait around 10 minutes for the boiler to complete its calibration.If the code returns, or the boiler still will not heat, stop and call a Gas Safe registered engineer. Do not open any gas components yourself.
The boiler has stopped itself while it tries to set its gas burning mix correctly, which usually means it needs a qualified engineer to check the flame sensing and flue before it can run safely again.
Full guide for EbYour boiler has shut itself down as a safety precaution because its burner is blocked, most likely due to a faulty temperature sensor sending it false readings, and it needs a qualified engineer to check it.
Full guide for 30Your boiler has shut itself down because it cannot read its water temperature properly, so it is stopping the burner as a safety precaution and will likely need a qualified engineer to restore heating and hot water.
Full guide for 38on the Viessmann Vitodens 200-W WB2C 26kW System
Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.
Call a Gas Safe engineer if…
- You can smell gas or see signs of a leak
- The Viessmann shows an Emergency or High severity code
- The boiler keeps locking out after repeated resets
- You've tried the DIY checks and the fault hasn't cleared
- There's visible water leaking from the boiler
- The flame is yellow or orange instead of blue