How to Test a Capacitor. Capacitors store energy to provide power to electrical appliances. The capacitors can, over time, lose their effectiveness to power the appliance. You can test them determine whether or not they are still good.
Remove the suspected faulty capacitor from the unit. If it's a high powered capacitor, it will still hold a high charge. Discharge the capacitor by using a metal screwdriver with a handle that's insulated. Touch the metal end of the screwdriver to both metal terminals at the same time to discharge any power left in them.
Turn on the capacitor tester and make sure it's getting power. Plug in the tester probes according to the instructions on the meter. Set the selector to an OHM scale before testing the capacitor. Some meters will have an OHM setting pre-set for you.
Touch the leads together so that the meter will zero out by adjusting the wheel on the meter.
Note where the meter points to before touching the wires to the capacitor. Then touch the terminals of the capacitor with the red probe, which will go on the left, and the black probe which will go on the right.
Watch the pointer on the meter. The needle should move away from the left side, or the infinity, and veer toward the right before returning to the infinity. It should move further to the right when the probes are reversed. This means the capacitor is good. If the needle goes all the way to the right side and doesn't return to the left, or infinity side, the capacitor is bad, or it has shorted out.