[Lifetime Warranty] 45 uF MFD ±5% 370/440 VAC 50/60 Hz Round Run Start Capacitor - Fits AC Motor Run, Fan Start, Heat Pump
45 uF 370/440 VAC round run capacitor for AC motors and heat pumps with BlueStars label.
BlueStars 45 uF 370/440 VAC round run capacitor with dimensions labeled 4.14 inches by 1.97 inches.
BlueStars 45 uF 370/440 VAC round run capacitor specification chart with technical details.
Diagram showing 2-terminal round run capacitor top view with C, F, and H terminal labels for AC motor and fan.
BlueStars 45 uF 370/440 VAC round run capacitor with aluminum case and metalized film construction details.
Educational infographic showing how to choose a 45 uF 370/440 VAC round run capacitor for AC and heat pump motors.
Technician installing a 45 uF 370/440 VAC round run capacitor into an AC condenser unit.
Technician installing a 45 uF 370/440 VAC round run start capacitor into an AC unit.
Infographic showing 45 uF run capacitor applications for air conditioners, refrigerators, heat pumps, and compressors.
Four-step infographic showing easy installation instructions for an AC motor run and fan start capacitor.
45 uF 370/440 VAC round run capacitor for AC motors and heat pumps with BlueStars label.
BlueStars 45 uF 370/440 VAC round run capacitor with dimensions labeled 4.14 inches by 1.97 inches.
BlueStars 45 uF 370/440 VAC round run capacitor specification chart with technical details.
Diagram showing 2-terminal round run capacitor top view with C, F, and H terminal labels for AC motor and fan.
BlueStars 45 uF 370/440 VAC round run capacitor with aluminum case and metalized film construction details.
Educational infographic showing how to choose a 45 uF 370/440 VAC round run capacitor for AC and heat pump motors.
Technician installing a 45 uF 370/440 VAC round run capacitor into an AC condenser unit.
Technician installing a 45 uF 370/440 VAC round run start capacitor into an AC unit.
Infographic showing 45 uF run capacitor applications for air conditioners, refrigerators, heat pumps, and compressors.
Four-step infographic showing easy installation instructions for an AC motor run and fan start capacitor.
Lifetime Warranty

[Lifetime Warranty] 45 uF MFD ±5% 370/440 VAC 50/60 Hz Round Run Start Capacitor - Fits AC Motor Run, Fan Start, Heat Pump

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45 uF/MFD 370-440VAC Round Run Start Capacitor

Key Features

  • Capacitance: 45 Microfarad (uF/MFD)
  • Tolerance: +/- 6%
  • Voltage Rating: Dual rated for 370 VAC or 440 VAC
  • Frequency: 50 / 60 Hz
  • Shape: Round
  • Case Material: Aluminum
  • Dielectric Material: Metalized Polypropylene
  • Terminals: 1/4 inch male quick-connect
  • Safety Standard: Meets EIA-456-A specifications
  • Operating Temperature: -40°C to 70°C

Replaces / Cross-Reference Part Numbers

  • Replaces any single-value round capacitor with matching 45 uF capacitance and either a 370V or 440V rating.
  • Universal replacement for capacitors used by brands such as Carrier, Goodman, Lennox, Rheem, Trane, York, and others.

Compatibility & Fitment

  • For continuous duty in single-phase motor applications.
  • Commonly used in air conditioner condenser units, heat pumps, and furnace blower motors.
  • Also used for compressor motors, fan motors, and refrigeration systems.

When to Replace

  • Motor hums but fails to start.
  • Fan requires a manual push to begin rotating.
  • AC compressor does not engage.
  • Visible damage to the existing capacitor, such as a bulging or swollen case, or leaking fluid.
  • Capacitance measures outside the specified tolerance when tested with a multimeter.

Installation Tips

  • Disconnect all electrical power to the unit before servicing.
  • Discharge the old capacitor by carefully shorting the terminals with an insulated-handle screwdriver or a discharge tool.
  • Confirm the new capacitor's uF rating matches the original part.
  • The voltage rating of the new capacitor must be equal to or higher than the original. A 440V capacitor can safely replace a 370V capacitor.
  • Note the wire positions on the original terminals before disconnecting.
  • Secure the new capacitor using the existing mounting bracket.
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  • Step 1

    Step 1

    Turn off the power and locate the capacitor
  • Step 2

    Step 2

    Discharge any stored electricity by shorting the terminals
  • Step 3

    Step 3

    Take a photo or note how the wires connect. Disconnect wires & install the new capacitor.
  • Step 4

    Step 4

    Reassemble and test

FAQ

This capacitor is intended to replace a round motor run capacitor with a 45 uF rating and a voltage rating of 370 VAC or 440 VAC. The microfarad value should match the original part exactly or stay within the stated ±5% tolerance. A 440 VAC capacitor is commonly used in place of a 370 VAC capacitor when the capacitance matches, but you should not replace a 45 uF capacitor with a different uF rating unless the equipment manufacturer specifically allows it.
A 45 uF round capacitor is commonly used in HVAC equipment including air conditioner condenser units, heat pumps, compressor motor circuits, and some fan motor applications. It may be used as a single run capacitor in systems that call for 45 uF, or alongside a separate fan capacitor depending on the equipment design. Always confirm the original capacitor's microfarad and voltage ratings and check whether your system uses a single capacitor or a dual-run style capacitor.
Common signs include the outdoor AC unit humming but not starting, a compressor that struggles to start, a fan motor that turns slowly or needs a push, intermittent shutdowns, breaker trips during startup, or weak cooling performance. In some cases the capacitor may appear swollen, leaking, or corroded at the terminals, but capacitors can also fail electrically without obvious external damage.
Check the label on the old capacitor for three key details: capacitance, voltage, and style. The capacitance should read 45 uF or 45 MFD, the voltage should be 370 or 440 VAC, and the body style should match your application if mounting space is limited. If you have a multimeter with capacitance testing, disconnect power, discharge the capacitor safely, remove at least one wire, and test the old part. If the reading falls outside the rated tolerance, replacement is usually recommended.
Installation is usually straightforward for someone familiar with HVAC electrical components, but capacitors can hold a dangerous charge even after power is off. Typical steps include shutting off power at the disconnect and breaker, confirming zero voltage with a meter, discharging the old capacitor safely, labeling the wires, swapping the part, and reinstalling the strap or bracket. Basic tools usually include a screwdriver, needle-nose pliers, and a multimeter. For an experienced technician, replacement often takes about 10 to 20 minutes.
Before installing a new capacitor, inspect the contactor, wiring terminals, and motor or compressor connections for heat damage, loose spades, or corrosion. If the old capacitor failed due to overheating, also check condenser coil cleanliness, motor amperage draw, supply voltage, and whether the fan blade or compressor is binding. A new capacitor may fail again quickly if the underlying motor or compressor problem is not corrected.
A run capacitor stays in the circuit while the motor is operating and helps maintain efficient running torque and performance. A start capacitor is used only briefly during startup and is then removed from the circuit by a relay or switch. This product's ratings and description indicate it is used for continuous-duty motor run applications, so it should only be used where the equipment specifies that type of capacitor.