ActronAir Indoor PCB AMIB provides indoor fan speed control, zone output switching, and wall controller communication for Classic Series 2 residential split ducted systems, forming the primary control interface between the wall controller, zone outputs, and refrigeration circuit. Board degradation typically presents as intermittent fault codes or erratic operation before complete failure -- complete loss of system operation and fault code display confirms the board rather than a sensor or wiring fault. Isolate power at mains before replacement -- live work on electrical components is dangerous and must only be performed by a qualified technician.