Your boiler is struggling to light the burner properly, which is preventing it from heating your water and radiators.

ignition

What causes this fault?

This fault occurs when the boiler's control board sends a signal to start the heating process, but it fails to detect a successful flame within the required timeframe. The most common reasons are a worn-out spark electrode that can no longer ignite the gas, or a faulty gas valve that isn't releasing enough fuel into the burner.