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How to check a run capacitor ?

Checking a run capacitor is important in maintaining the proper functioning of motors and other electrical devices. A run capacitor is often used in single-phase induction motors to improve their performance. Here are the steps to check a run capacitor:

Tools and Equipment Needed:

  1. Multimeter with capacitance measurement capability
  2. Insulated screwdriver or other suitable tool for discharging the capacitor


1. Safety Precautions:

  • Before attempting to check the capacitor, ensure that power to the equipment is turned off and disconnected.
  • Use appropriate personal protective equipment, especially when working with electrical components.

2. Discharge the Capacitor:

  • Capacitors can store electrical energy even after the power is disconnected. Use an insulated screwdriver to short the terminals of the capacitor to discharge any stored charge.
  • Be cautious to avoid electrical shocks during this step.

3. Remove the Capacitor:

  • If the capacitor is not easily accessible, remove it from the equipment. Note the connections to ensure correct reinstallation.

4. Set the Multimeter:

  • Set the multimeter to the capacitance measurement mode. This is usually denoted by the symbol “μF” or a similar capacitor symbol.

5. Measure Capacitance:

  • Connect the multimeter leads to the terminals of the capacitor.
  • For non-polarized capacitors, the order of connection doesn’t matter. For polarized capacitors, observe the polarity markings on the capacitor and connect the positive lead of the multimeter to the corresponding terminal.
  • The multimeter will display the capacitance value.

Interpret the Reading:

  • If the measured capacitance is within the specified tolerance range (usually indicated on the capacitor or in the device’s documentation), the capacitor is likely in good condition.
  • If the capacitance is significantly lower than the rated value, the capacitor may be faulty and should be replaced.
  • If the capacitance is significantly higher than the rated value, the capacitor may be internally shorted and should be replaced.

Additional Checks (Optional):

  • Some multimeters have an additional mode for checking the capacitor’s resistance. A very high resistance or an open circuit reading could indicate a faulty capacitor.
  • Visual inspection: Look for any signs of physical damage, such as bulging or leaking.


  • Capacitors can fail in different ways, and a capacitance measurement alone may not reveal all issues. In some cases, specialized capacitor testing equipment may be required for a more comprehensive assessment.

Following these steps will help you check the run capacitor and determine if it is functioning within the specified parameters. Replace any capacitor that shows signs of damage or falls outside the acceptable capacitance range.

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