To test a capacitor to see if it is working, you will first need an ohmmeter/multimeter. You will be taking a measurement/reading of the electrical resistance. The reading on your multimeter will tell you if the capacitor is working properly or needs to be replaced. Please Note: This procedure for testing to see if a capacitor is good is meant for appliance troubleshooting such as a refrigerator run start capacitor with only 2 leads.
To test an appliance capacitor:
Be sure power is turned off to the appliance and unplugged from the wall. This needs to be done when you remove any type of capacitor from any type of appliance. Once the appliance is unplugged, wait about 30 minutes after removing power before you pull the capacitor out. A capacitor on any appliance such as a refrigerator run start, washing machine motor, or microwave oven, can hold a lethal electrical charge. Waiting 30 minutes or longer will lessen the risk before you remove it. Take the capacitor out of the appliance making sure not to make contact with the leads. Depending on the type of appliance you are working on, you may need to discharge the power from the capacitor. Here is a step-by-step procedure for how to discharge a capacitor.
NOTE: At times, some older types of capacitors will not need to be tested with a multimeter. This is because when some capacitors go bad, they will bulge out. You only need to do a quick visual check to see if this is the case. If the capacitor in your refrigerator is bulging, then it has gone bad and you will need to replace it.
Once you have the capacitor out, use your multimeter to see if the capacitor is in working condition. First, be sure to set your multimeter to ohms. Some multimeters have more settings, so to be exact somewhere over 10k and 1m ohms or select a higher setting of ohms. Use the same procedure whether you are using an analog meter or digital multimeter as you are testing for electrical resistance. Next, take the multimeter leads and put the black lead to the negative side of the capacitor and the red lead to the positive side. The writing or markings on the capacitor leads will most likely be a (+) and a (-). The (+) is obviously the positive, and the (-) is the negative. Once you have the leads on the capacitor, have a look at the meter reading. If the meter shows zero (0) and then moves slowly towards infinite, then the capacitor is working and does NOT need to be replaced. If the multimeter reading stays at zero (0) and does not move at all, then this indicates the capacitor is not working (open capacitor) and needs to be replaced. If the meter reading shows a very low resistance, the capacitor is shorted out. If you need to replace your refrigerator capacitor, there are many available online for less.
This method of testing refrigerator capacitors will work on all models of refrigerators such as GE, Whirlpool, Frigidaire, Samsung, LG, Maytag, Kenmore, and many others.
WARNING – When you replace a capacitor make ABSOLUTE sure to replace it with one that is the exact same value or a higher value. DO NOT use a capacitor with a lesser value.
What is an ohm?
The ohm is defined as a resistance between two points of a conductor.
To read more about what an ohm is, see the Wiki page on the definition of the ohm. (Symbol: Ω)
This method of testing a capacitor is meant for appliance capacitors such as in refrigerators. The same method above will work for almost any type of capacitor but we are focusing on repairing appliances.