Automotive alternating generator systems provide electrical power to the primary ignition system and the secondary accessory systems through a negative grounded battery. The alternator is an improvement on previous generator systems and is designed to put out up to 15 amps of power under a full load. Several components of an alternator can wear out and fail, usually requiring replacement of the entire unit as most alternators are not user serviceable. The average backyard mechanic can replace and alternator in about 1 hour.

Test the Output

When an alternator wears out, it does so in stages. An alternator produces power by rotating three plates across a winding of copper wires. These plates can fail one at a time and reduce, but not stop, the power output. As more plates fail, the power drops to levels that will eventually cause the battery to die and the ignition system to fail. Testing the output regularly with a voltage tester while the car is running can give indications that these plates, or other components, are wearing out.