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The Goodman B1789857 Piston Kit is a genuine OEM refrigerant metering piston (flowrator) for the ASZ130241AH 13 SEER, 2‑ton (24,000 BTU) R‑410A heat pump. The piston seats in the liquid-line fitting and provides the precise orifice restriction that meters refrigerant into the indoor or outdoor coil, setting the correct superheat and subcooling for rated capacity and efficiency.
OEM vs. Generic: Piston orifice diameter is measured in thousandths of an inch and is matched to the exact indoor/outdoor coil pairing. A generic piston of the wrong bore starves or floods the coil, killing capacity and risking compressor damage. OEM ensures the drilled size matches Goodman's AHRI-certified combination.
Install difficulty: Advanced (4/5). Requires recovering refrigerant, opening the liquid-line flare/fitting, swapping the piston and O-ring, then evacuating and recharging. EPA-certified technician recommended.