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17-30 ELECTRICAL SYSTEM
Charging System
Alternator Inspection
There are three t ypes of alternator failures: short, open,
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 electromag-
netic field, or just by aging, will result in low output.
•
To check the alternator output voltage, perform the follow-
ing procedures.
○
Disconnect the alternator connector [A].
○
Connect a hand tester [B] as shown in the table.
○
Start the engine.
○
Run it at the rpm given in the table.
○
Note the voltage readings (total 3 measurements).
Alternator Output Vo ltage
Connections
Reading
Tester Range
Tester (+) to Tester (–) to @3 000 rpm
250 V AC One black lead
Another black
lead
38 ∼ 58 V
If the output voltage is within the values in the table, the
alternator is operating correctly, and the regulator/rectifier
is damaged. A m uch lower reading indicates that the al-
ternator is defective.
•
Check the stator coil resistance as follows:
○
Stop the engine.
○
Disconnect the alternator connector.
○
Connect a hand tester as shown in the table.
○
Note the readings (total 3 measurement).
Stator Coil Resistance @20°C (68°F)
Connections
Tester Range
Tester (+) to Tester (–) to
Reading
×1Ω One black lead
Another black
lead
0.29 ∼ 0.43 Ω
If there is more resistance than shown in the table, or no
reading (infinity) for any two leads, the stator has an open
and m ust be replaced. Much less resistance means the
stator is shorted and must be replaced.
•
Using the highest resistance range of the hand tester,
measure the resistance between each of the black leads
and chassis ground.
Any reading less than infinity (∞) indicates a short, neces-
sitating stator replacement.
If the stator coils have normal resistance, but the voltage
check shows the alternator to be defective; then the rotor
magnetism has probably weakened, and the rotor must
be replaced.
Special Tool - Hand Tester: 57001-1394