Ensure a jumper cable is attached to both alternator ground points
when attaching cables from test stand G- terminals.
Ensure a jumper cable is attached to both alternator 28V B+
terminals when attaching cables from test stand G+ terminals.
Connect cables from both alternator ground terminals to test stand G- terminal.
Connect cables from both alternator positive terminals to test stand G+ terminal.
Connect cable from alternator regulator IGN to test stand F terminal.
Connect 28 VDC output and 14 VDC output to test stand.
Auxiliary voltage and current meters may be required to measure
14 VDC output.
Fabricate a jumper wire with a ring terminal at both ends. Connect test stand wire from IGNITION
SWITCH terminal to F-B terminal.
Ensure auxiliary measuring equipment is properly grounded to test
stand. Failure to do so may lead to erroneous readings or damage to
Prior to operation of test stand, ensure all switches and controls are in
initial positions as referenced in Operator and Maintenance Manual,
TM 9-4910-663-12 (UMC Model GSAR-500), or Operator and
Maintenance Manual, TM 9-4910-485-12 (Sun Model AGT-9/9A).
Set test stand as follows:
(a) DC ammeter load and starter selector
(b) DC ammeter field and battery charge selector
(c) Field circuit switch
(d) DC voltmeter circuit selector
(e) Connect DC voltmeter (0-50 VDC) from point between regulator 14 VDC output and load in
14 volt circuit (or 14 volt battery).
Connect ammeter (0-75 ADC) in load line from 14 V regulator to 14 V load.
Turn test stand master power switch and master load switch to ON, and turn battery switch to
24 VDC. Green lamp on test stand must illuminate.
Perform no-load test. Set test stand battery circuit selector to 24 VDC, IGN switch to ON, and start
varidrive. Observing the DC voltmeter output voltage and tachometer rpm, increase speed until
tachometer reads 5000 rpm. Record voltmeter reading and refer to table 18-5, No-Load Test, for
When tachometer reaches 3000 rpm, green lamp should go off
indicating proper charging from alternator.
Normal voltage range is 26-30 VDC. High amperage is +10
percent over the rated alternator output of 364 amps at 5000 rpm.
Perform no-load test. Increase alternator speed to 5000 rpm; record results. Refer to table 18-5,
No-Load Test, for diagnosis.
18-3.1. 400-AMPERE DUAL VOLTAGE ALTERNATOR TESTING AND REPAIR (Cont'd)