BoilerFaultCodesTechnical description
Warm start sensor interruption (ecomax 800) / False light (flame signal present but gas valve closed)
What causes this fault?
This fault occurs when the boiler's sensors detect a flame signal even though the gas valve should be closed and the burner turned off. The most common reason is a faulty ionisation probe sending a false electrical signal to the control board, or a gas valve that is slightly leaking or failing to close fully. In some cases, moisture on the internal electronics or a failing circuit board can also trick the system into thinking a flame is present.
This fault can sometimes be more frequent during periods of high humidity or heavy rain, as moisture ingress can affect the sensitive electrical signals between the probe and the control board.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.