Komatsu 830E-AC Shop Manual page 249

6. Set the voltmeter to the diode test scale.
a. Connect the black lead of the voltmeter to
pin E in the wiring harness plug.
b. Connect the red lead to the (B-) terminal on
the alternator.
c. The voltmeter must read a voltage drop.
d. Reverse the leads. The voltmeter must read
OL.
e. If there is no voltage drop, the alternator is
defective.
f. If there is a voltage drop, proceed to Step 7.
7. Install a jumper from the alternator (B+) terminal
to pin F in the wiring harness plug.
a. Momentarily (1 second), connect a jumper
wire from pin A to the alternator (B-) terminal.
b. Again, touch the shaft with a steel tool to
detect significant magnetism. Is the shaft
magnetized?
c. If the shaft is not magnetized, the alternator
is defective.
d. If the shaft is magnetized, the regulator is
defective.
Regulator Bypass Test (Amp Rating)
1. Disconnect alternator-to-regulator wiring har-
ness plug (1, Figure 10-9).
2. Connect a jumper wire from pin F (F+ terminal)
in the alternator-to-regulator harness plug to the
alternator (B+) terminal.
3. Start the engine and accelerate to high idle.
4. Momentarily touch pin A (F- terminal) wiring
harness plug to the alternator ground terminal
(B-). Observe whether the amps increase or
decrease.
a. If the amps increase to within ± 10% of the
rated output when connecting (F-) to ground
(B-), the alternator is good. Refer to Table
10-4.
b. If the amps decrease when disconnecting
pin A (F-) from alternator ground (B-), the
alternator is good. Refer to Table 10-4.
D10003 07/06
Limit the time the terminal is connected to a few
seconds. Doing so can protect the charging sys-
tem from excessive voltage increase.
Table 10-4: REGULATOR BYPASS TEST
Connect
Amps increase Amps
No change
Battery Charging Alternator
Disconnect Diagnosis
Alternator is good.
Replace the regula-
decrease
tor only if low amps/
low Volts are indi-
cated by Bench Test
1 or 2.
No change The alternator must
be repaired. Go to
Static Tests.
D10-19