MARS 12921 Run Capacitor

The MARS 12921 Run Capacitor is a fundamental component for maintaining the efficiency of single-phase electric motors in HVAC and refrigeration systems. This 40 MFD 370V oval run capacitor is engineered for continuous duty, providing the necessary phase shift to keep compressors and fan motors running cool and stable. Built to UL 810 standards, it features a non-PCB, oil-filled aluminum construction and a patented internal pressure sensitive interrupter (PSI) designed to safely disconnect the capacitor in the event of an internal failure. As a high-reliability JARD motor run capacitor, the 12921 is a direct replacement for 40 uF 370 VAC oval units from brands like GE Genteq and Supco. Techs rely on its 1/4-inch male quick-connect terminals for fast field installation and its broad operating temperature range of -40°C to +70°C, ensuring consistent performance in demanding environmental conditions.

• Universal Compatibility: Serves as a versatile 40 microfarad 370vac oval run capacitor replacement for various residential and commercial HVAC brands.
• Safety First Construction: Features a physical interrupter and non-PCB oil to meet rigorous safety protocols.
• High Tolerance: Maintains a capacitance tolerance of +/- 6%, ensuring precise motor torque and energy efficiency.
• Industrial Durability: The aluminum case dissipates heat effectively, extending the service life of the motor it supports.

Can I use a 440V capacitor to replace this 370V model?
Yes, in modern HVAC service, a higher voltage rating is an acceptable upgrade as long as the 40 MFD capacitance remains identical. However, you cannot go lower than the original 370V rating.

What are the symptoms of a failing 40 MFD run capacitor?
Common signs include a motor "humming" but failing to start, intermittent cycling, or a physically bulged capacitor casing. Replacing a weak capacitor early prevents permanent winding damage to the compressor.

How do I ensure this oval capacitor fits my existing bracket?
The MARS 12921 features standard oval dimensions (approximately 2.125 inches by 2.056 inches at the base); if your original bracket is for a round capacitor, a universal mounting strap may be required.

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.