Your boiler has encountered an internal electronic communication error that is preventing it from running safely.

Flow temperature too high. Primary sensor overheated.

What causes this fault?

This fault occurs when the boiler's internal computer brain fails to communicate properly with the other sensors and components inside the unit. It is usually caused by a physical failure of the main circuit board or a loose connection in the internal wiring harness that prevents data from traveling through the system. Because the boiler cannot verify that it is operating safely, it stops running as a protective measure.