Run Capacitor vs. Start Capacitor

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All capacitors are designed to store energy. The difference lies in what this energy is stored and used for.

If you’re having an issue with your air conditioning system, the capacitor could be the cause, but which one do you need for your repair?

When it comes to air conditioning, there are two main types of capacitors, run capacitors and start capacitors. The differences between a run capacitor and a start capacitor can be bewildering. However, with a clear understanding of what each type of capacitor is, this confusion can easily be resolved.

Run Capacitors

Run capacitors are more commonly used in air conditioning systems than start capacitors. The run capacitor in your AC is used to store energy, which is used to turn the fan motor, an essential component to your working AC. Without the run capacitor, the fan cannot turn.

Start Capacitors

Start capacitors are the second most commonly found capacitor within an AC system. Without a start capacitor, your AC will not start up at all, as it is the start capacitor that provides the initial energy needed for start-up. A lot of torque is necessary to start up an AC system, so a start capacitor will have greater capacitance than a run capacitor.

AC Capacitors

The term “AC capacitor” usually refers to your air conditioners run capacitor, simply because run capacitors are more commonly found in air conditioning systems. If you have a faulty run capacitor, your AC system will fail to cool your home properly or efficiently, resulting in wasted energy and money. If you have a faulty start capacitor, your AC may not run at all.

There are several key signs to look out for that might indicate that your AC capacitor is faulty.

  • Your AC no longer blows cold air
  • Your AC creates a low humming sound that wasn’t there before
  • Your energy bills have been increasing
  • Your AC sometimes does not turn on, or does not turn on at all
  • Your AC turns off unexpectedly

Remember, if you are unsure if your AC capacitor needs replacing, you can use a multimeter to test your AC capacitor. 

Generator Capacitor

Similarly to all the capacitors described above, a generator capacitor also stores electric charge. The generator capacitor provides the voltage, and regulates the voltage, within the generator. A low voltage reading may indicate that the generator capacitor is faulty.

You can test your generator capacitor using a multimeter.

Refrigerator Capacitor

A refrigerator capacitor most often refers to the more common run capacitor in a fridge.

The run capacitor in your fridge is likely to be located near the compressor, so signs that the run capacitor in your fridge might be faulty include:

  • Hearing a clicking sound when the refrigerator compressor runs
  • The refrigerator compressor seems to be running too often (a few times an hour is normal, more when in frequent use)
  • The refrigerator compressor does not seem to be running often enough

Replace Your Run Capacitor with Repair Clinic

Repair clinic has the guidance and parts you need to easily replace your run capacitor or start capacitor, in your AC, generator or refrigerator.


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