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PART NUMBER · ICE O MATIC

Ice O Matic 9181003-19 Start Capacitor

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The 9181003-19 is a start capacitor for Ice O Matic equipment. It gives the motor a boost of electrical power to help it start up.

By the HVAC Fitter teamUpdated Oct 22, 2026

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Start capacitors show a rating range rather than a single number. This part assists the motor during startup and is not a run capacitor.

Safety first. Turn off power at the breaker and the outdoor disconnect before touching any components. Test for power to make sure the circuit is completely dead. A capacitor can hold a charge even with the power off. It must be discharged with an insulated tool before anyone touches its terminals.

Specifications

FROM THE PART LISTINGS
  • Part number: 9181003-19
  • Brand: Ice O Matic
  • Part type: Capacitor
  • Capacitance: 145-174uF
  • Frequency: 50/60HZ
  • Height: 2.5 in / 6.35 cm
  • Length: 4.95 in / 12.57 cm
  • Voltage: 250VAC
  • Width: 2.8 in / 7.11 cm
MATCH THESE NUMBERS ON YOUR OLD CAPACITOR
  • µF (MFD): must be the same, like 45/5
  • Volts: same or higher (440 can replace 370)
  • Shape: round or oval, to fit the bracket

From the maker's and parts sellers' listings for this number. Compare them with the label on your old part.

How a Start Capacitor Works

Motors need extra torque to start turning from a full stop. A start capacitor provides that initial push to get the motor moving. Once the motor is running, the start capacitor is taken out of the circuit.

A start capacitor is different from a run capacitor. A start capacitor shows a capacitance range and stays in the circuit only for a few seconds during startup. A run capacitor stays connected to keep motors running smooth.

Understanding the 9181003-19 Specs

Every capacitor has electrical and physical ratings printed on its outer case. These ratings must be matched closely to keep the equipment running properly.

  • Capacitance: 145-174uF. This rating is given as a range, which identifies it as a start capacitor.
  • Voltage: 250VAC. The replacement voltage rating must be the same or higher.
  • Frequency: 50/60HZ.
  • Length: 4.95 in / 12.57 cm.
  • Width: 2.8 in / 7.11 cm.
  • Height: 2.5 in / 6.35 cm.

Signs of a Weak or Failed Capacitor

When a capacitor fails, the motor cannot get the extra push it needs to begin turning. A motor or fan that hums but will not spin is often a bad capacitor, not a bad motor.

Capacitors can also fail physically. You might see bulging, swelling, or leaking fluid on the casing. If the motor tries to start, hums, and shuts down, the start capacitor may be weak or bad.

How to Replace the Part Safely

Always put safety first when working with high-voltage parts. Take your time and make sure no power is present before you begin.

  1. Shut off electrical power at the main breaker and any disconnect switch.
  2. Test the unit with a meter to verify the power is off.
  3. Discharge the capacitor across the terminals using an insulated tool.
  4. Take a photo of every wire before removing anything.
  5. Disconnect the old capacitor and make sure the new part fits the mounting bracket securely.
  6. Move wires one at a time to the same spots on the new part, using your photo as a guide.

Read your old part

  1. Look at the label on your existing part and locate the number 9181003-19.
  2. Check that the capacitance rating reads 145-174uF or MFD.
  3. Verify the voltage rating shows 250VAC.
  4. Check the outer dimensions of 4.95 in / 12.57 cm length, 2.8 in / 7.11 cm width, and 2.5 in / 6.35 cm height to ensure it fits your bracket.

When to call a pro

Hire a licensed HVAC technician for any step you are not sure you can do safely. If you do not have the proper tools to test voltage and discharge the capacitor, stop and call a professional.

Questions

What does the 145-174uF rating mean?

It indicates the microfarad rating, also written as MFD or uF. A rating shown as a range identifies the unit as a start capacitor rather than a run capacitor.

Can I replace a capacitor with a higher voltage rating?

Yes. Capacitor voltage must be the same or higher. For example, a 440 V capacitor can replace a 370 V one, but never the other way.

Why does my motor hum but not start?

A fan or motor that hums but will not spin is often caused by a bad capacitor, not a bad motor. The capacitor may no longer have the strength to give the motor its starting push.

Is the 9181003-19 a dual run capacitor?

No. A dual run capacitor powers two motors from one can and has three terminals marked HERM, FAN, and C. The 9181003-19 is a start capacitor.

Related part numbers

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  • 12788Capacitor, MarsSame part type
  • 9161124-02Condenser Fan Motor, Ice-O-MaticSame brand
  • 9181003-26Capacitor Reference, Ice-O-MaticSame part type
  • 12783Capacitor, MarsSame part type
  • 9101170-02Relay Reference Guide, Ice-O-MaticSame brand
  • 9181009-09Capacitor Reference, Ice-O-MaticSame part type

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