TM 9-4940-549-14&P
NOTE
While checking voltage at V2, check to
see if the reading varies when the ca-
ble or the connector plug on the alter-
nator cover assembly is disturbed. This
could indicate inadequate test connec-
tions which must be corrected before pro-
ceeding with the tests.
(b) If voltage at V2 is low or zero, the alternator positive and
negative output circuits must be tested as indicated in
steps (4) and (5) below.
(4) Test alternator positive output circuit as follows:
(a) Check voltage at V3 as shown in figures 7-8 and 7-9.
(b) If voltage is zero, check fuse.
(c) If voltage is greater than zero, but below voltage V1 fig-
ure 7-10 check for poor circuit conditions between battery
positive terminal and alternator positive output terminal.
(d) Correct any discrepancies before proceeding with operational
tests.
(e) If voltage indicated is equal to voltage V1, test alternator
negative output circuit as directed in step (5) below.
(5) Test alternator output circuit as follows:
(a) Check voltage V4 as indicated in figures 7-10 and 7-12.
(b) If voltage is below voltage at V1 (fig. 7-10), check for
inadequate circuit conditions between battery negative ter-
minal and alternator negative output terminal.
(c) Correct any discrepancies before conducting operational
tests.
(6) Conduct excitation voltage test as follows:
(a) With voltmeter connected as in figure 7-11, close switch.
(b) Voltmeter should indicate 3.5
(c) If voltmeter indicates zero volts, test voltage regulator as
directed in step (7) below.
(d) If voltmeter indication is greater than 3.7 Vdc, test for
open circuit of alternator field (rotor) as directed in step
(8) below.
7-22
