How to Discharge a Capacitor

Before working on any motor, be sure you discharge the capacitor. Capacitors store energy and can pack a serious and potentially dangerous jolt of electricity.

Difficulty: Moderate

Instructions

Things You'll Need:

• Alligator Clips
• Slotted Screwdrivers

1. Unplug the power feeding the motor.

2. Pick up a 20,000-ohm, 2-watt wire resistor at an electronics store. Be sure it's a wire-wound resistor.

3. Stick a jumper on each end of the resistor, using two jumpers with alligator clips.

4. Clip one free end of a jumper to the flat edge of a standard screwdriver with an insulated handle.

5. Attach the final jumper to one terminal of the capacitor.

6. Touch the tip of the screwdriver to the other terminal.

Tips & Warnings

• If there are more than two terminals on the capacitor, be sure to attach the clip to each one and discharge all of them.
• If you don't fully understand this procedure or it makes you uncomfortable or you're unsure if you did it correctly, consult a licensed electrician.

[Westek17]

on 9/21/2008 Wire 3 or 4 [good] 60 watt incandescent light bulbs in SERIES (not parallel) then discharge for 30 seconds. Then affirm 0vdc across cap with DVM.

[KOwen]

on 7/10/2007 How can I find a 2 watt 20K ohm resistor? I have not found a single place that sells them.

on 11/22/2005 Do not use a screwdriver or other bare metal on a large capacity capacitor. Doing so will literally disintegrate the conductor. It will also produce a large bang with enough force to throw you to the ground. In addition to this being a bad idea for pretty much any sized capacitor (because of the danger), it will also likely damage your capacitor.

on 11/22/2005 A capacitor, with a good charge on it, can blow a notch in the screwdriver. The screwdriver can actually weld itself to the terminal. Use a resistor and jumpers.

on 11/22/2005 just put your screwdriver across the terminals and it will discharge. no need to buy a capacitor. (make sure your screwdriver has an insulated handle!)