(The best way to test a capacitor is to replace it with a new one of the same rating).
I. TESTING CAPACITORS USING AN OHMMETER:
a. Disconnect the power to the unit.
b. Use an insulated screwdriver to shunt between the capacitor terminals to discharge it. Then remove the capacitor from the circuit.
c. Set the ohmmeter on its highest scale.
d. Touch the two capacitor terminals with the two leads from the meter. If the capacitor is in good condition, the meter should register zero ohms and then move slowly back toward infinity.
e. Switch the leads and repeat step d to get the same results. Otherwise, replace the capacitor.
The needle should deflect to infinity and stay there from the very beginning if the capacitor is open. The needle should register 0 Ω and stay there if the capacitor is shorted.
II. TESTING CAPACITORS USING A DIGITAL CAPACITOR TESTER (They are inexpensive and very accurate.)
a. Disconnect power from the unit.
b. Discharge the capacitor as in Ib above.
c. Turn on the digital tester and connect its leads to the capacitor terminals. This will show the exact capacitance of the capacitor in microfarads. Compare the reading shown on the meter with the capacitor rating printed on its side.
d. If it is below what it should be, the capacitor is weak and it must be replaced.
e. If the meter registers no reading, it will mean there is a disconnection in the capacitor, and it must be replaced.
III. TESTING CAPACITORS USING A TEST LIGHT (See fig. 66)
a. Disconnect power to the unit.
b. Discharge the capacitor as in Ib above.
c. Check the mfd rating on the capacitor and set the test light selector switch for that range.
d. Connect the test leads to the capacitor terminals.
e. Turn on the tester. The indicator light should glow dimly and go out.
f. If the light stays on, it will mean that the capacitor is shorted, and it must be replaced.
g. If the light never comes on, there is a disconnection in the capacitor and it must be replaced.
