Your boiler's internal computer has encountered a critical error or is having trouble communicating with its electronic security card, causing the system to shut down for safety.

Burner blocked. Strong interference (EMC) field nearby; alternatively boiler coding card or main PCB faulty. Remove EMC interference. If the equipment will not restart, check the boiler coding card and replace, or replace the control unit.

What causes this fault?

This fault occurs when the boiler's main control board loses its connection with the small electronic chip that tells it how to operate safely. It is usually caused by electrical interference, a loose chip connection, or a physical failure within the central circuit board itself. Because the boiler no longer knows its own safety parameters, it shuts down immediately to prevent damage.