What are the specs for this Piston?

The correct replacement for Goodman model ASZ130181AE — B1789851 is this exact part. It is the factory-specified replacement with exact OEM specifications. Using a part with different specifications can cause equipment damage or void your warranty. You can verify this by checking the data plate on your Goodman equipment which lists the model number ASZ130181AE — B1789851.

What symptoms indicate I need a new piston?

Common symptoms that indicate you need a new piston include unusual noises, intermittent operation, complete failure to operate, or visible damage. For specific diagnostic guidance, visit nationalhvacparts.com/pages/hvac-diagnostic.

Is this piston compatible with Bryant or Payne systems too?

Many Goodman parts are cross-compatible with Bryant and Payne systems since all three brands are manufactured by Carrier Global Corporation. The same physical part is often used across multiple brand labels with different model numbers. To verify cross-compatibility, check your Bryant or Payne equipment service manual for cross-compatible part numbers, or contact info@nationalhvacparts.com with your model number for confirmation.

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Goodman

OEM Goodman Piston / Flowrator Kit for ASZ130181AE — B1789851

Name: OEM Goodman Piston / Flowrator Kit for ASZ130181AE — B1789851
Brand: Goodman
SKU: GOODMAN-B1789851
Price: 5.95 USD
Availability: InStock

SKU: GOODMAN-B1789851 Brand: Goodman

$5.95 $7.95

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Goodman B1789851 Piston Kit

The Goodman B1789851 is a factory-original refrigerant metering piston (flowrator) kit for the ASZ130181AE 13 SEER, 1.5-ton heat pump. The piston is a fixed-orifice metering device that controls refrigerant flow into the coil, setting the system's superheat and subcooling. The precise orifice bore is matched to the unit's tonnage and refrigerant — even a small deviation changes capacity and efficiency, so using the exact factory piston is essential for correct operation.

Specifications

OEM Part Number: B1789851
Fits: Goodman ASZ130181AE heat pump
Type: Fixed-orifice piston / flowrator metering device
Function: Meters refrigerant into the coil at the correct rate
Includes: Piston (installs into existing flowrator body)

OEM vs. Generic

The genuine Goodman piston is bored to the exact orifice size the ASZ13 was engineered around. An incorrect bore — even one size off — causes flooding or starvation, poor capacity, high energy use, and possible compressor damage. Because the part is inexpensive and its orifice is capacity-critical, OEM is the only reliable choice.

Installation Difficulty

Advanced (5/5). The piston sits inside the sealed refrigerant circuit at the flowrator body. Replacement requires refrigerant recovery, opening the flowrator, seating the correct piston, and evacuating/recharging the system. EPA Section 608 certification required.

This is a sealed-system component — installation must be performed by an EPA-certified HVAC technician using proper recovery and charging equipment.

Shipping Information

Orders placed before 3PM CST ship same business day
Standard delivery: 2-5 business days
Express shipping available at checkout
Free shipping on orders over $75
Tracking number emailed upon shipment

Return Policy

30-day returns on unused parts in original packaging
Electrical parts (capacitors, contactors, control boards) are final sale once installed
Email info@nationalhvacparts.com to initiate a return
Refunds processed within 5-7 business days

OEM Goodman Piston / Flowrator K...

$5.95

Frequently Asked Questions

Does this Piston fit my Goodman ASZ130181AE — B1789851?

Yes. This is the factory-specified OEM piston for the Goodman ASZ130181AE — B1789851. It is a direct drop-in replacement that fits without modification. Always verify the model number on your equipment nameplate before ordering.

How do I replace the piston on my Goodman ASZ130181AE — B1789851?

Refer to your equipment service manual for model-specific steps. General approach: turn off power, photograph connections, remove old part, install new part, restore power and test. For gas components, hire a licensed technician. Email info@nationalhvacparts.com for guidance.

What symptoms mean I need a new piston?

Common symptoms: unusual noises, intermittent operation, complete failure, or visible damage. Visit our diagnostic hub for symptom-based troubleshooting.

Is this piston compatible with Bryant or Payne too?

Many Goodman parts are cross-compatible with Bryant and Payne since all three brands are manufactured by Carrier Global Corporation. The same physical part is often used across brand labels with different model numbers. To verify: check your Bryant or Payne equipment service manual for cross-compatible part numbers, or email info@nationalhvacparts.com with your model number.

Should I use OEM or aftermarket for my Goodman piston?

OEM recommended for reliability and warranty compatibility. OEM parts match exact factory specifications for proper fit, performance, and safety. While aftermarket alternatives cost less upfront, the risk of improper fit and reduced lifespan usually makes OEM the better value long-term.

How fast does National HVAC Parts ship?

Orders placed before 3:00 PM CST ship the same business day. Standard delivery is 2–5 business days anywhere in the continental United States. Express shipping available at checkout. We ship from Houston, TX to all 50 states. 30-day return policy on all parts.

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