ActronAir Standard Residential Outdoor PCB R410A (D4CPU-P) is the factory-fitted D4CPU-P outdoor control board for R410A Classic Series and commercial package residential split ducted systems including PCA and SRA series, managing compressor staging, outdoor fan speed, high and low pressure protection, and defrost logic for R410A refrigerant systems. A failed D4CPU-P board causes complete system lockout -- the compressor will not run and cannot be reset until a genuine replacement is installed -- fit the 100% Genuine ActronAir 2020-045B to restore factory outdoor control. Isolate power at mains before replacement -- live work on electrical components is dangerous and must only be performed by a qualified technician.