ANSWERS: 1
  • An alternator is a key piece of an automotive electrical system. While the battery provides startup power and an electrical grounding point, the alternator supplies the automobile with electrical energy while the engine is running. When an alternator fails, the automobile will only run as long as the battery has an electrical charge, so replacing a faulty alternator is an important step in keeping an automobile properly maintained.

    Alternator Differences

    In principle, most alternators work in the same way: an electromagnetic field is generated when permanent magnets are moved across an electrical coil. In practice, though, automotive alternators are not interchangeable. An older (pre-1985) automobile may use an alternator with a lower power rating than those used by newer automobiles. For example, an alternator for a 1975 Ford F-100 pickup truck is capable of producing approximately 60 amperes of electrical current. Since the engines for many trucks built in the 1970s were carburated and used a mechanically timed ignition system, 60 amperes was enough electrical current for the automotive electrical system to operate properly. By way of comparison, a 2005 Ford F-150 pickup requires a 110-ampere alternator. A 2005 Ford F-150 pickup truck uses a fuel-injected engine with an electronic ignition system. In addition, many automobiles sold since the 1990s come with electric windows, stereo systems and power locks as standard equipment. Because a vehicle such as the 2005 F-150 has greater electrical needs than a vehicle manufactured in the 1970s, a more robust alternator is needed to supply the automotive electrical system with enough energy.

    Changing the Alternator

    Before attempting to remove the alternator from the automobile, disconnect the battery from the battery cables. This will prevent any electrical energy from flowing through the electrical system while you are working on the vehicle. An alternator is usually connected to the automotive electrical system with four wires. Each wire connects to a labeled terminal: "B" for the wire that provides electrical energy to the battery; "IG" for the ignition input wire that supplies power for the alternator/regulator assembly; "S" for the probe wire that monitors charging voltage at the battery terminal; "L" for the output wire to the "Alternator" warning lamp. To avoid reconnecting the wires to the wrong terminals, mark each wire with a piece of tape and a pen or marker before removing the wires from the terminals. Remove each wire from its respective alternator terminal, and remove the retaining bolts holding the alternator to the alternator retaining frame. Slip the alternator belt (or serpentine belt, if so equipped) off the alternator pulley, and remove the alternator from the vehicle. Install the wires on to their respective terminals on the new alternator. Install the new alternator into the alternator retaining frame, and install the alternator retaining bolts, leaving the bolts loose enough to adjust the alternator as necessary. Slip the alternator (or serpentine) belt on to the alternator pulley, and adjust the alternator so that the belt is tight. Tighten the retaining bolts.

    Source:

    AutoZone website: 1975 Ford F-100 alternator specifications

    AutoZone website: 2005 Ford F-150 alternator specifications

    Autoshop101 Website: Understanding the Alternator (PDF)

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