What does a bad capacitor reading look like?

When testing a residential HVAC capacitor with a digital multimeter set to the microfarad (uF) scale, a bad or failing capacitor reading will show a capacitance value that drops significantly—more than ten percent—below the microfarad rating printed on the component's manufacturer label. For example, if you are testing a dual-run capacitor rated at 35 microfarads and your multimeter displays a reading of 28 microfarads or lower, the internal dielectric material and foil layers have degraded beyond acceptable limits. In cases where the capacitor is completely dead or short-circuited internally, the multimeter may read zero, display an "OL" (open loop) error, or fail to register any stable numerical value at all. You can verify an accurate reading by ensuring power is disconnected, the capacitor is fully discharged, and all wire terminals are isolated before touching your multimeter probes to the contacts.