MARS 12789 Run Capacitor

The MARS 12789 is a heavy-duty 45/7.5 MFD 440V round dual run capacitor engineered for continuous duty in residential and light commercial condensing units. This JARD series component features a metallized polypropylene film dielectric housed in a non-PCB, oil-filled aluminum canister, ensuring efficient heat dissipation during high-ambient operations. Designed to support both the compressor (45 microfarad) and the condenser fan motor (7.5 microfarad), it provides the necessary phase shift for split-phase motors to maintain optimal torque and energy efficiency. The 440VAC rating offers a robust safety margin, making it a reliable universal replacement for systems originally spec'd with 370V or 440V components. With a physical footprint of approximately 2 inches in diameter and a case height of 3.88 inches, it integrates seamlessly into standard electrical capacitor strap mounts. The 1/4-inch quick-connect terminals are clearly marked for "C," "HERM," and "FAN" to streamline field installation and prevent wiring errors.

Key Benefits:

• Dual-Capacitance Logic: Consolidates the starter and run functions for both the compressor and fan into a single space-saving round profile.
• Universal Voltage Compatibility: Rated for 440VAC, allowing it to safely replace 370V capacitors without risk of dielectric breakdown.
• Thermal Resilience: Operates efficiently within a wide temperature range of -40°F to 158°F, critical for rooftop and sun-exposed equipment.
• Contractor-Grade Construction: Features a pressure-sensitive interrupter and a rust-resistant aluminum housing for long-term structural integrity.
• Standardized Fit: 12789 MARS specifications match most OEM requirements for 45+7.5 uF dual-run applications.

Common Questions:

Can I use a 440V capacitor if my old one was 370V?
Yes. In HVACR applications, you can always increase the voltage rating (e.g., using a 440V to replace a 370V), as this provides a higher insulation threshold. You must, however, match the 45/7.5 microfarad rating exactly (+/- 6% tolerance).

What are the signs that a MARS 12789 needs replacement?
Common electrical indicators include a "humming" compressor that fails to start, the outdoor fan motor not spinning, or visible physical symptoms such as a "domed" or bulging top on the aluminum canister. Testing with a multimeter should show readings within 6% of the 45 and 7.5 MFD ratings.

Are the terminal connections interchangeable?
No. For proper motor rotation and torque, the "HERM" terminal must connect to the compressor's start winding, the "FAN" terminal to the fan motor, and "C" to the common line. Reversing "HERM" and "FAN" can lead to immediate motor failure.

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Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.