Komatsu 930E-2, Shop Manual

Page: 578 / 739

BENCH TEST
Results of on-vehicle test should be confirmed by
these bench tests, if possible.
When it is not possible to perform on-vehicle test,
alternator performance can be checked quickly by
referring to these bench tests.
Equipment:
Test Bench, with 15 – 20 Hp motor
set up to drive alternator to 7000 RPM.
Voltmeter, 0 – 40 Volt Range
Ammeter, 0 – 400 Amp Range
Mount alternator on test bench according to the bench
manufacturer’s instructions. Refer to Figure 13-1 for
set-up to measure voltage and amperage produced by
alternator. Voltage /- .2V of regulator setpoint
is “normal”. Amperage /- 10% of rated output
at 5000 rpm is “high”.
TEST 1 - NO-LOAD TEST
Without electrical load but with battery connected, run
alternator at 5000 rpm. Refer to Table 13-3 below.
Table 13-3. NO-LOAD TEST
AMPS VOLTS DIAGNOSIS
HIGH LOW
Test bench battery is discharged
(or defective).
Allow to charge or replace.
HIGH NORMAL
Give time to stabilize while
monitoring VOLTS. If VOLTS rise
above normal range (Table 13-2)
regulator and/or field coil must be
replaced. If AMPS fall, charging
system is OK.
HIGH HIGH
Stop test. Regulator and/or field
coil should be replaced.
(Go to Static Tests.)
LOW LOW
Alternator and/or regulator must
be repaired or replaced.
Go to Test 3.
LOW NORMAL Regulator OK. Go to Test 2.
LOW HIGH
Stop test. Bench malfunction or
wiring error.
TEST 2 - FULL LOAD TEST
With load set to rated output (nameplate) +/- 10%, run
alternator at 5000 rpm. Refer to Table 13-4.
Table 13-4. FULL-LOAD TEST
AMPS VOLTS DIAGNOSIS
HIGH LOW
Test bench battery is discharged
(or defective).
Allow to charge or replace.
HIGH NORMAL Charging system OK.
HIGH HIGH
Stop test. Regulator and/or field
coil should be replaced.
(Go to Static Tests.)
LOW LOW
Alternator and/or regulator must
be repaired or replaced.
Go to Test 3.
LOW NORMAL Increase load.
LOW HIGH
Stop test. Bench malfunction or
wiring error.
TEST 3 - REGULATOR BYPASS TEST
Perform this test only when suggested by other tests.
Alternator connections and load same as test 2. By-
pass regulator as shown in Figure 13-3. Note whether
amps rise to within +/- 10% of output rating when
connecting F- terminal to ground. Note whether amps
fall when disconnecting F- terminal. Then refer to
Table 13-5 below.
Limit terminal connection to a few seconds in
order to protect charging system from excessive
voltage rise.
Table 13-5. REGULATOR BYPASS TEST
CONNECT DISCONNECT DIAGNOSIS
Amps Rise Amps Fall
Alternator is OK.
See note, replace
regulator only if low
AMPS/low VOLTS
indicated in Test 1
and/or Test 2.
No Change No Change
Alternator must be
repaired. Go to Static
Tests.
Note: Before replacing regulator, check continuity of
energize circuit (refer to Static Tests, Test 5).
M13-8 Niehoff Alternator Overhaul Manual M13003 04/01