How To Attach A Capacitor To A Sump Pump Motor

Most of the time, when your sump pump makes a humming sound, you would think that the motor got frozen or got burned. However, there is also another issue that can cause this humming sound—a bad capacitor.

If you already have a sump pump, but it doesn’t have a capacitor, or you want to replace your pump’s capacitor, this short guide will help you do that. Follow these easy steps to know how to attach a capacitor to a sump pump motor.

On a side note, sometimes a simple capacitor replacement can save you the cost of a new motor.

That’s why the first thing you should check is the capacitor. With that being said, here are steps you need to follow to successfully replace and attach a capacitor to a sump pump motor.

Attaching A Capacitor To A Sump Pump Motor

  • Turn of the power to your sump pump. And for maximum safety, you should also turn off the power at the circuit breaker. 
  • Depending on the make of the sump pump, the capacitor will either be under the pump cover or on top of the motor. It can also be under the electrical end of the motor. Check the manual to find the capacitor’s precise location.
  • Keep in mind that sump pumps will have both a run capacitor and a start capacitor. The rating of a start capacitor will be around 50-400 MFD & 125, and for the run capacitor, it will generally be 15-50 MFD & 370 VAC.
  • Whatever the case, you will find that the covers are held on using multiple screws. Remove them, take off the cover and you will see the capacitor.
  • You will see the capacitor and size will be around the roll of half dollars.
  • Don’t touch the capacitor yet. A full pump capacitor stores an electrical charge and shock you even when you turn off the power.
  • Before removing the capacitor, you need to discharge the energy. You can do this by placing a screwdriver in the middle of the capacitor and across the leads.
  • Hold on. Did you know that capacitors are known to explode when shorted out? For your protection, wear safety gear like goggles, helmets, or eye protection.
  • If the capacitor is at the end of the pool pump, remove the screws that are holding it in place. You will notice that there is a plastic cover on top of the capacitor. When you replace it and place a new one, it will have to be in the same position. This is there to prevent shorting out the motor.
  • Remove the leads and take a picture so that you can restore them when you add in a new capacitor and reconnect them.
  • With the capacitor in place, it’s time to connect the moto leads to the sump pump capacitor and secure the capacitor in place as require. Also, watch the placement of the plastic strip, as previously mentioned.
  • Place the cover as it was. Tighten the screws and reestablish the power at the circuit breaker.


Before you add a new capacitor, you should check the rating for replacement specifications. This will vary from manufacturer to manufacturer. Always look for their MFD or UF and also VAC specs.

Also, try to replace a bad capacitor with an identical capacitor. You can go higher, but you should never use a lower-rated capacitor. And that’s how to attach a capacitor to a sump pump motor. If you still have any questions, feel free to leave a comment down below.

About the Author Juan Williams

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