Like any job, you need the right tools. First, search online using the model number of your unit for the specifications of the capacitor. You may be able to locate a schematic of the unit online that will give you the specification of the capacitor. Next, see if the capacitor is out of specification. You may need to buy a Fluke 101 or similar meter if you don't have one so you can read the capacitance. The units will be microfarads. Replace if out of specification. Go where the Pros go to buy it so you don't get hosed.