Static Tests; Field Coil Tests; Check For Open Field Coil; Check Function Of Clamping Diode - Komatsu 930E-2 Shop Manual

STATIC TESTS

Static tests are performed on the partially disas-
sembled alternator to confirm component failure
indicated by on-vehicle test or bench tests.
EQUIPMENT:
Ohmmeter, Simpson 260 or equivalent
Regulator Tester, or Ohmmeter
Diode Tester or Ohmmeter
Remove control box cover and drive pulley. Discon-
nect regulator from control unit. Remove cover plate.
Disconnect all phase leads attached to the front hous-
ing ("P1" through "P6" in Figure 13-6).
NOTE: Refer to disassembly procedures in Alternator
Disassembly section of this manual. Before repairing
the alternator, perform all static tests.
REGULATOR TESTS
The regulator is normally checked using a regulator
tester. If a regulator tester is used, make connections
to regulator plug as follows (see Figure 13-4 for wire
assignments):
NOTE: Terminal locations differ on SAE and metri-
pack connectors.
• Wire 1 to "Field Coil (-)"
• Wire 2 to "Ground"
• Wire 3 to "Field Coil (+)" or "B+"
• Wire 4 to "Ignition" or "B+"
Refer to regulator tester manufacturer's instructions
for test procedure.
If regulator tester is not available, it is difficult to test
regulator for open output transistor. However, most
regulator failures are caused by shorted output tran-
sistor, so the following procedure utilizing an ohmme-
ter, will often suffice when a regulator tester is not
available.
TEST 1 -
Check For Shorted Output Transistor
Set ohmmeter to x100 scale and make sure ohmmeter
is zeroed. Using the regulator connector plug, connect
one ohmmeter lead to terminal "F-", connect to other
lead to terminal "B-", and observe meter reading.
Reverse leads and observe meter reading. In one
direction the meter should read less than 600 ohms.
In the other direction the ohmmeter should read very
high. If ohmmeter reads zero in both directions, output
transistor is shorted and regulator must be replaced.
M13003 04/01
TEST 2 - Check Function Of Clamping Diode
Set ohmmeter to x100 scale and make sure ohmmeter
is zeroed. Using the regulator connector plug, connect
one ohmmeter lead to terminal "F-", connect the other
lead to terminal "B-" and observe ohmmeter reading.
Reverse leads and observe meter reading. In one
direction the ohmmeter should read less than 600
ohms. In the other direction the ohmmeter should read
very high. If the ohmmeter reads less than 600 ohms
in both directions (short) or very high in both directions
(open) clamping diode is defective and regulator must
be replaced.
Note: If regulator failure is indicated, field coil failure
must also be suspected.

FIELD COIL TESTS

TEST 3 - Check For Open Field Coil
Set ohmmeter to x1 scale and make sure ohmmeter is
zeroed. Connect one ohmmeter lead to "B+" output
stud. (NOTE: On unit with "F+" stud, connect ohmme-
ter to "F+" stud). Connect the other lead to terminal
"F-" of control unit harness. Ohmmeter should read
less than 3 ohms. If ohmmeter reads above the speci-
fied limit, the field coil is open and must be replaced
(replace or repair Stator & Shell Assembly).
1. Ignition (E)
(Harness Lead #4)
2. Relay (R)
3. Terminal Block
4. F- (Harness Lead #1)
Niehoff Alternator Overhaul Manual
FIGURE 13-4.
5. F+ (Harness Lead #3)
6. Ground Wire from Reg.
(Harness Lead #2)
7. B+ Buss Leads to
Rectifier
M13-9