Alternator conversion kits are kits that allow the replacement of the electrical generators used in older cars and trucks with more modern alternator systems. While both generators and alternators produce electricity for the car, generators are larger than alternators, less reliable and have varying power outputs depending on engine speed. In contrast, alternators produce relatively constant amounts of power at any engine speed, allowing the battery to charge and electrical systems to function normally even when the idling the engine.
The impetus behind an alternator conversion is often a failing generator, though some owners of older vehicles may prefer to replace their existing generator with an alternator simply for the reliability advantages that alternators provide. Alternators have higher reliability than generators, since their internal brushes do not need to handle the full current produced by the alternator, unlike generators. Alternators also tend to have higher power outputs than generators.
Some older vehicles originally used early alternator designs with external voltage regulators that are not as efficient or reliable as modern alternators that use internal voltage regulators. Earlier alternators using mechanical voltage regulators also sometimes suffer from pulsating power levels when the engine is idle, but modern alternators using an electronic voltage regulator produce constant power levels even at idle. Using an alternator conversion kit to upgrade the alternator to a more modern design is an option for owners of many of these vehicles.