Capacitors work by acting as tiny temporary batteries. They essentially store power, as a battery does. A major difference is that most capacitors store their energy for just short time; when the electricity is no longer feeding them, within seconds they discharge. A larger, specialized capacitor that provides a significant boost to starting an engine may keep its power for a much longer time.
Capacitors rarely go bad, but when they do, they need to be replaced. This is not something you can do in a home repair setting; it requires specialized equipment for soldering a new one on and testing it. Older capacitors look like miniature soda cans about the size of rice grains. They stand upright and are various colors. Many times when one such as this goes bad it bulges at the sides, becomes discolored and may even leak liquids.
New-style capacitors do not give any indication when they go bad. A GE Profile range may develop any one of a number of problems that can be traced back to a faulty circuit board. Many times the quickest and least expensive answer is to replace the entire board as opposed to trying to track down the individual problem or capacitor on the board. The GE Profile circuitry is easy to get to, and replacing the board with a known good one takes a few minutes.
Capacitors can go bad from a variety of reasons. The insides are complex, and even a tiny error in the manufacturing process can lead to one that is destined to have a short life. Excessive heat can lead to failure, so if you have a Profile that has faulty insulation, it may overheat the circuit board. A power surge or spike in electricity can also overwhelm a capacitor with too much electricity.