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BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS
8A - 15
CASE GROUND
FIELD
TERMINALS
BATTERY
VOLTAGE
_ J
-J2-DB—'
IGNITION SWITCH
[
GROUND
^ B A T T E R Y VOLTAGE
1Si—
1
_L
ALTERNATOR
CASE
GROUND
ALTERNATOR
BATTERY
TERMINAL
ENGINE
CONTROLLER
LESS THAN
JUMPER WIRE
TO GROUND
TEST
VOLTMETER
TEST
AAAMETER
BBS
DISCONNECTED
ALTERNATOR
GROUND
OUTPUT
MES
A C C I
CARBON PILE
RHEOSTAT
l a
CHASSIS "
GROUND
J908A-14
CURRENT OUTPUT TEST
C u r r e n t o u t p u t test determines w h e t h e r or not a l -
ternator is capable o f d e l i v e r i n g i t s r a t e d c u r r e n t
output.
PREPARATION
(1) Before s t a r t i n g any tests m a k e sure vehicle has
a f u l l y charged battery. Test a n d procedures on how
to check for a f u l l y charged b a t t e r y are shown i n
B a t t e r y section o f t h i s Group.
(2) Disconnect b a t t e r y negative cable.
(3) Disconnect a l t e r n a t o r o u t p u t w i r e a t the alter-
nator battery t e r m i n a l .
(4) Connect a 0-150 ampere scale D.C. ammeter i n
series between a l t e r n a t o r B A T t e r m i n a l a n d discon-
nected a l t e r n a t o r o u t p u t w i r e (Fig. 2). Connect Posi-
t i v e lead to a l t e r n a t o r B A T t e r m i n a l a n d negative
lead t o disconnected a l t e r n a t o r o u t p u t w i r e .
(5) Connect positive lead o f a test v o l t m e t e r (range
0-18 volts m i n i m u m ) to a l t e r n a t o r B A T t e r m i n a l .
(6) Connect negative lead o f test v o l t m e t e r t o a
good ground.
(7) Connect a n engine tachometer a n d reconnect
battery negative cable.
(8) Connect a variable carbon pile rheostat (C3950)
between b a t t e r y t e r m i n a l s . Be sure carbon pile is i n
Fig. 1 Alternator Output Wire Resistance Test (Typical)
Open or O f f position before connecting leads. See
Battery section, Load Testing for instructions.
(9) Remove a i r hose between Engine Controller and
air cleaner.
(10) Connect one end o f a J u m p e r W i r e to ground
and w i t h other and probe green R3 lead w i r e at back
of alternator (Fig. 2). (This w i l l generate a fault
code).
CAUTION: Do not connect blue J2 lead of wiring to
ground. Refer to Group 8W - Wiring Diagrams for
more information.
TEST
(1) S t a r t engine. I m m e d i a t e l y after s t a r t i n g reduce
engine speed t o idle.
(2) Adjust carbon pile and engine speed i n incre-
ments u n t i l a speed o f 1250 r p m and voltmeter read-
i n g of 15 volts is obtained.
CAUTION: Do not allow voltage meter to read above
16 volts.
(3) T h e ammeter r e a d i n g m u s t be w i t h i n l i m i t s
shown i n alternator specifications i n back o f this
group for t h a t size o f alternator being tested.
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