Komatsu 4D98 Series Shop Manual page 153

10.1.5 Inspection and overhaul
(1) Diode
10. Alternator
The diode makes the current flow only in
the direction shown in Fig. 8. Check elec-
trical continuity between two terminals (for
example, terminals BAT and U) using a
tester as shown in Fig. 9 and, if they are
continuity, the diode is acceptable. If not,
the diode is damaged. The diode is ac-
ceptable if two terminals are not continuity
when the tester is connected in the re-
verse manner. The diode is damaged if
they are continuity.
If even a single diode is faulty as a result of
the above measurements, replace the en-
tire diode assembly.
Tester leads
X@ e
Q
/ - /
co?Euity I
c3 I Continuity I - I
Checking (+) diode
Checking (-) diode
Note:
Never use a high-voltage insulation ohmmeter
such as a megger for testing. Otherwise, the
diode may be damaged.
(2) Rotor
(a) Wear limit for slip spring
Measure the outside diameter of the slip
spring. If wear exceeding 1 mm from the
standard size is measured, replace the ro-
tor assembly.
Standard: 27 mm, Wear limit: 26 mm
(b) Check of slip ring surface
Check that the slip ring surface is smooth
and free from contamination by oil, etc. If
the surface is rough, polish using #500 to
#600 emery cloth. If it is dirty, clean using
alcohol.
u
V
w @
C
0 0
diode
AT
T
E
diode
Fig. 8
Tester leads
I
Q
1 coKuity / - I
Tester
Fig. 9
Fig. 10
1
1 o-7