How to Discharge an Air Conditioner Capacitor


Air conditioner compressor and fan motors use large capacitors to help the motors start under load. These high voltage, high-capacitance devices can hold a lethal charge for days or months after the unit is disconnected. Before testing, changing or disconnecting an air conditioner capacitor, you must ensure it is first discharged. A tool called a grounding rod will safely discharge a capacitor in an air conditioner or other high voltage appliance.

Things You'll Need

  • Safety glasses
  • Grounding rod
  • Screwdriver with insulated handle
  • Turn off power to the air conditioner unit at its disconnect switch. Put on safety glasses. Connect the wire lead on the grounding rod to the air conditioner's green chassis ground lug screw. Loosen the lug and place the lead connector beneath the ground lug and tighten the terminal firmly.

  • Touch the probe to one terminal of the capacitor and hold it there for 20 seconds. Repeat this step for each terminal on the air conditioner's capacitor. Some air conditioner units place two capacitors inside one housing. These capacitors have three terminals.

  • Hold the screwdriver by the insulated handle. Touch the tip of the screwdriver to a capacitor terminal, then allow the screwdriver shaft to touch another terminal. A charged capacitor will cause a spark, but the capacitor will also discharge. Do this for all three terminals. This ensures the capacitor is fully discharged to earth ground.

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