Service Manual — page 595 of 715

Text on this page

ELECTRICAL SYSTEM 16-35
Charging System
Alternator Inspection
  There are three types of alternator failures: short, open
(wire burned out), or loss in rotor magnetism. A short or
open in one of the coil wires will result in either a low output,
or no output at all. A loss in rotor magnetism, which may be
caused by dropping or hitting the alternator, by leaving it
near an electromagnetic field, or just by aging, will result in
low output.

• To check the alternator output voltage, do the following
  procedures.
○Turn the ignition switch off.
○Remove the left fuel tank cover (see Fuel Tank Cover Re-
 moval in the Frame chapter).
○Disconnect the alternator lead connector [A].
○Connect a tester as shown in the table 1.
○Start the engine.
○Run it at the rpm given in the table 1.
○Note the voltage readings (total 3 measurements).
Table 1: Alternator Output Voltage           @4 000 r/min (rpm)
                  Connections
                                                  Reading
      Tester (+) to        Tester (–) to
    One White lead      Another White lead    AC 48 V or more
 If the output voltage shows the value in the table, the al-
 ternator operates properly.
 If the output voltage shows a much lower reading than
 that given in the table, stop the engine and inspect the
 stator coil resistance.
•Check the stator coil resistance as follows.
○Stop the engine.
○Connect the tester as shown in the table 2.
○Note the readings (total 3 measurement).
Table 2: Stator Coil Resistance                   @20°C (68°F)
                  Connections
                                                  Reading
      Tester (+) to        Tester (–) to
    One White lead      Another White lead      0.11 ∼ 0.17 Ω

    If there is more resistance than shown in the table, or
    no tester reading (infinity) for any two leads, the stator
    has an open lead and must be replaced. Much less than
    this resistance means the stator is shorted, and must be
    replaced.
•   Measure the resistance between each of the black leads
    and chassis ground.
    Any tester reading less than infinity (∞) indicates a short,
    necessitating stator replacement.
    If the stator coils have normal resistance, but the voltage
    check showed the alternator to be defective; then the rotor
    magnets have probably weakened, and the rotor must be
    replaced.