How to Tell If a Capacitor Failed
- 1). Turn off the electrical equipment's power supply. If the electrical equipment hard wires directly to a circuit breaker, turn off the appropriate circuit breaker. If the electrical equipment uses a plug and wall receptacle, pull the plug from the wall receptacle. If batteries power the electrical equipment, either disconnect the battery terminals or pull the battery from the equipment.
- 2). Look for an oily or crusty film on the capacitor's housing. Sometimes the capacitor heats to the point where the leaking electrolyte -- the oily film -- dries and forms a crusty coating on the capacitor's case. If the capacitor leaks its electrolyte, the capacitor has failed or will fail soon.
- 3). Check the capacitor for a swollen or bulging housing near the wire terminals. A swollen or bulging capacitor housing indicates the capacitor has overheated and its internal plates touch. A capacitor with a swollen or bulging case has failed or will fail soon.
- 4). Disconnect the capacitor's wire terminals from the electrical equipment. Grip the wire connectors with needle-nose pliers and pull the connector off the terminals.
- 5). Lay a screwdriver across the capacitor's terminals. This relieves the capacitor's stored charge.
- 6). Determine the capacitor's capacitance rating, using the label on the capacitor's housing as a guide.
- 7). Turn a multimeter to its capacitance setting, if equipped. Not every multimeter contains a capacitance setting.
- 8). Touch the multimeter's probes on the capacitor's wire terminals and compare the multimeter's capacitance reading to the capacitor's capacitance rating. The capacitor has failed if the multimeter's reading and the capacitor's capacitance rating exceeds a 6 percent differential.
- 9). Turn the multimeter to its resistance setting.
- 10
Watch the multimeter's readout screen and touch the multimeter's probes to the capacitor's wire terminals. The multimeter's readout should jump to infinite briefly, then drop. If the readout remains at infinite, the capacitor has failed.
