Komatsu 830E-AC Shop Manual page 258

TROUBLESHOOTING TIPS
PROBLEM
1. Installed the alternator and connected the
cables (B+/B-(GND)) but the alternator has no
output. What could be wrong?
Refer to the Regulator Bypass test (No Output)
section for additional testing information.
2. Self-energizing alternator loses residual
magnetism.
Refer to the Regulator Bypass test (No Output)
section for additional testing information.
3. How can voltage regulators be tested?
Refer to the Regulator Bypass test (No Output)
section for additional testing information.
D10-28
A self-energizing type alternator can lose its residual magne-
tism and not work properly. Residual magnetism is the small
amount of magnetic field that remains in the alternator when
there is no field current present. This residual magnetism is
necessary to start the alternator. Once established, the resid-
ual magnetism slowly declines over time when the alternator
is not used. In practical terms, this time period is months. To
test for the presence of residual magnetism, touch a steel
wrench or screwdriver to the rotor shaft on the anti-drive end
of the alternator. If a light magnetic attraction is present, the
residual magnetism is present. If there is no attraction, the
residual magnetism is lost and must be restored or the alter-
nator may not self-energize. See 2. Self-energizing alternator
loses residual magnetism.
Once an alternator is magnetized at the factory, it must hold
its residual magnetic field for the duration of its life. In rare
instances, residual magnetism can be lost either during an
extended period of inactivity (shelf time) or if the alternator
was exposed to a strong external magnetic field.
Momentarily (1 second), connect a jumper wire from the
jumper (D+) terminal on the regulator to the (B+) alternator
output terminal. The alternator must operate normally. If not,
further troubleshooting is required.
Voltage regulators can be tested using several methods.
1. The first method is to remove the suspect regulator and
substitute a known good regulator and then conduct the
alternator output test. If the alternator performs properly,
the suspect regulator is confirmed defective and must
be replaced.
2. The second method, incorporating the process of elimi-
nation, is to follow a diagnostic sequence and test the
individual alternator component functions to determine if
the components are good or bad. After systematically
eliminating the alternator components as the cause of
the problem, most likely, the regulator is defective.
Replace the regulator.
3. The third method involves utilizing a direct regulator
tester which is commercially available. When using a
tester to test a regulator, follow the instructions supplied
by the tester manufacturer and service manual for
proper terminal connections. If the regulator is not prop-
erly connected, the tester or the regulator may be dam-
aged. Refer to the regulator tester manufacturer's
instructions to determine if the regulator is defective.
Battery Charging Alternator
CAUSE/SOLUTION
D10003 07/06