How To Test a Heat Pump Capacitor

Capacitors are basically the same, regardless of type or manufacturer, but Vishay Sprague and Kemet are particularly known for their capacitor technology and the use of new electronic components and multilayer electronic parts. Sprague specializes in tantalum capacitors, while Kemet offers everything from tantalum capacitors to ceramic, film and aluminum electrolytic units, which are generally smaller in size but have a high capacitance and are made of cathode aluminum foil, electrolytic paper, and with aluminum oxide film acting as the dielectric.

A heat pump compressor capacitor’s function is to provide the pump motor with the needed boost of electricity for the starting torque when a working load has been placed on the unit. But, over time, the capacitor might lose its efficiency, and the electrical boost will be too weak for the heat pump to function properly. This would mean that the heat pump will try to compensate for this by working harder, and it would begin to use up more electricity. There are a few steps you can follow to know if your heat pump capacitor is still working properly:

  1. Make sure that the power to your unit is turned off. Use needle-nose pliers to remove the electrical connections from the capacitor and lift it out. Capacitors hold a charge, and while the charge might not be enough to kill you, it can still give you a serious shock, so you can begin by removing the remaining charge from your capacitor with the help of a digital multi-meter.
  2. Look at the selector switch on the meter and make sure that the dial points at “volt,” then touch the red and black probe ends of the meter to the capacitor’s bare metal electrical connectors. The meter might give you some kind of reading, but just keep touching the probes to the capacitor’s electrical connectors until the voltage runs out.
  3. Point the dial on the meter’s selector switch to the capacitor tester. Like you did when you discharged the capacitor, touch the red and black probe ends to the connectors. The meter will give you a reading, which will register as either ‘good’ or ‘bad’ in the LCD display. If you want to use an analog meter to test your capacitor, substitute this for the previous step:
    1. Switch the dial on the analog meter to point at “ohms.”
  4. Touch the red and black probes to the capacitor’s electrical connectors and hold them in place for two seconds. The capacitor, if it were working properly, would have stolen a charge from the battery of your analog meter.
  5. After two seconds, lift the probes away from the electrical connectors and change the order of the meter’s connection with the capacitor: Place the black probe on the connector previously touched by the red probe, and the red probe on the one previously touched by the black probe. Read the meter the instant you place the probes on the connectors. Just for a moment, the needle in your analog meter should jump to the right to show that the capacitor has been able to store a charge.
  6. You can do this test, touching the probes to the capacitor’s electrical connectors for two seconds and reversing the connection, as many times as you want until you’re satisfied. If the needle doesn’t jump, it means that the capacitor isn’t properly storing a charge and could be faulty.

If the capacitor is bulged or leaking, then it’s broken. Don’t touch the liquid from the capacitor, as it is toxic, and dispose of the capacitor accordingly.


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