An automotive charging system is made up of three major components: the battery, the voltage regulator and an alternator. The alternator works with the battery to generate power for the electrical components of a vehicle, like the interior and exterior lights, and the instrument panel. An alternator gets its name from the term alternating current (AC).
Alternators are typically found near the front of the engine and are driven by the crankshaft, which converts the pistons' up-and-down movement into circular movement. (To learn more about the basic parts of car engines, read How Car Engines Work.) Some early model vehicles used a separate drive belt from the crankshaft pulley to the alternator pulley, but most cars today have a serpentine belt, or one belt that drives all components that rely on crankshaft power. Most alternators are mounted using brackets that bolt to a specific point on the engine. One of the brackets is usually a fixed point, while the other is adjustable to tighten the drive belt.

Voltage Regulation:
    As you already know from the 'wire' page, all wire has resistance. You also know that when you have current flow through a resistive element (wire), there will be a voltage loss. If the current draw from the charging system was constant, there would be no need for a voltage regulator. If there was no loss, the design engineer would simply design the alternator to produce a given voltage. This won't work with a car audio system because the current draw is anything but constant. This means that the alternator needs a compensating voltage regulator. The voltage regulator controls the flow of current in the rotor's windings. The voltage regulator's output current will typically be between 0 amps (with little or no current draw) and 5 amps (at maximum current draw). The regulator can vary the current flow infinitely to keep the voltage precisely at the target voltage. Generally the regulator is built into the alternator. There are some high current/special use alternators which may have external regulators. Some of the external regulators are adjustable via a potentiometer.

Current demand and flow:
If you have an alternator that can produce 120 amps of current (max) and the the total current demand from the electrical accessories (including the battery) is only 20 amps, the alternator will only produce the necessary current (20 amps) to maintain the target voltage (which is determined by the alternator's internal voltage regulator). Remember that the alternator monitors the electrical system's voltage. If the voltage starts to fall below the target voltage (approximately 13.8 volts depending on the alternator's design), the alternator produces more current to keep the voltage up. When the demand for current is low, the full current capacity of the alternator is not used/produced (a 120 amp alternator does not continuously produce 120 amps unless there is a sufficient current draw).

Dimming lights:
When you play your system at very high volumes and the lights on your vehicle dim slightly, it generally means that your alternator can not supply enough current for all of your electrical accessories (including your amplifiers). If you play a long bass note/tone and the lights get dim and stay dim until the note is over, your alternator clearly can not keep up with the current demand. If, on a long bass note, the lights dim just for a fraction of a second but return to their original brightness while the note/tone is still playing, the alternator's regulator may just be a little slow in reacting to the voltage drop. Since the lights return to their original brightness during the bass note, the alternator is able to supply the current needed by your power your amplifiers and other electrical accessories.
Voltage Regulation
Main Cause of Charging System Inactive

Before discussing the preventive maintenance and diagnostic procedures for the charging system, were going to cover certain environmental and product application factors that can cause the charging system to malfunction.

Excessive heat. An alternator can become damaged if it operates too long at excessive temperatures. Damaging heat levels are generated in two ways: when the alternator becomes dirty either externally or internally restricting its ability to dissipate heat from its external surface or not allowing air to pass through the unit, and when air ducts and heat shields are not replaced after the alternator has been serviced.

Dirt and dust. Charging system components operate less efficiently when buildup of dirt particles form around wire and cable connection points. Dirty connection points impair the flow of electrical current.

Vibration. If charging system components are poorly or loosely mounted to the vehicles frame, the resulting vibration can damage sensitive internal components. A loosely mounted component will also diminish the performance of the important belt drives. This is very important on high powered engines.

If you Wash your car if your alternator is I.C Type.PLEASE pack the I.C of your                 Alternator.Because that is so sensitive.

Automotive Alternator Performance Test

Alternator Performance Test. Connect voltmeter to alternator terminals and ammeter to alternators positive output cable, per Figure 13. Make sure ammeter is at least 6 inches (15 cm) away from alternator to eliminate the possibility of faulty readings. Make sure voltage is present at alternators output terminals. Start engine and run it at 1500 RPMs (operating RPM). Check that all vehicle loads are turned off and reading on ammeter is less than 20 amps. If ammeter reading is greater than 20 amps double check that all vehicle loads are turned off and that batteries are fully charged. Record voltage on voltmeter. Reading should be between 13.8 & 14.4 v for a 12 volt system, 27.8 & 28.4 v for 24 volt systems. If the voltage is not within these ranges then try adjusting the regulator if available. If the regulator can not be adjusted alternator is defective.

Alternator Performance Test Under Load. Keep engine running at 1500 RPM (operating RPM) and meters are connected per Figure 13. Turn on vehicle loads until 75% of the alternator�s rated output is achieved on ammeter display. Record voltage on voltmeter. Compare reading to that taking during the Alternator Performance Test. If alternator voltage drops more than .5 volts for a 12 V system and .7 volts for a 24 V system then alternator is defective. An alternative method of putting load on an alternator is with a carbon pile tester. Connect carbon pile tester across batteries. Adjust carbon pile until desired reading is obtained on ammeter. Record voltage on voltmeter and shut off vehicle.

Alternator Cable Test. To test the positive cable connect the ammeter to the positive cable from the alternator. Make sure the ammeter is at least 6 inches (15 cm) away from the alternator to eliminate the possibility of faulty readings. Connect the voltmeter’s negative lead to the positive terminal of the alternator and the positive lead to the positive terminal on the battery, see Figure 14. Start engine and set engine RPM to 1500 RPMs (operating speed). Turn on vehicle loads until 75% of alternator’s rated output is achieved on ammeter display. If necessary use a carbon pile tester to apply load on alternator. Record voltage on voltmeter. If reading is greater than .25 volts in a 12 volt circuit or .50 volts in a 24 volt circuit check all wire connections and cable connections. If reading is less than .25 volts in 12 volt circuit and .50 volts in a 24 volt circuit cables are good. Turn off vehicle loads and shut off engine. To test the negative cable move voltmeter’s negative lead to the negative terminal of the battery and the positive lead to the negative terminal of the alternator, see Figure 15. Run test again. Use Figure 16 for recommended wire sizes for any cable repairs.

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