How you can test an electrolytic capacitor if you do not have an ESR meter or leakage tester at hand. This is the way I originally learned this in electronics school. This is not a foolproof method, but will catch basic defects, such a a shorted, open, or very leaky capacitor. It will not, for example, show if a capacitor breaks down under a certain voltage; the ohmmeter only supplies a low testing voltage. At such low voltage, the capacitor might not leak.
If the capacitor is still in the circuit, at least one end will have to be disconnected from the circuit. Also, do not touch the metal of the probes while doing the testing. Since the electrolytic capacitor is polarized and always has some inherent leakage, the leakage will be greater in one direction than the other. As a precautionary measure, the capacitor should be discharged before testing by shorting across the terminals to make sure no charge remains.
When the ohmmeter is first connected across the capacitor, the needle should move toward the low-resistance (meaning toward zero) end of the scale. As the capacitor charges, the needle should move back up toward the high-resistance end of the scale.
If the needle does not move during the testing, the capacitor is open. If the meter drops toward zero and stays there, then it is shorted. If the meter reads low in both directions it might be leaky. Discharge the capacitor and do the test again. Also, having new capacitors on hand for comparison would help.
