Charging System Resistance Tests; Charging System; Current Output Test - Jeep 1997 Grand Cherokee Service Manual

FIELD TERMINALS
B+ (OUTPUT TERMINAL)
GROUND TERMINAL
ZG
DIAGNOSIS AND TESTING (Continued)
(5) Inspect generator drive belt condition and ten-
sion. Tighten or replace belt as required. Refer to
Belt Tension Specifications in Group 7, Cooling Sys-
tem.
(6) Inspect automatic belt tensioner (if equipped).
Refer to Group 7, Cooling System for information.
(7) Inspect connections at generator field, battery
output, and ground terminals. Also check ground con-
nection at engine. They should all be clean and tight.
Repair as required.

CHARGING SYSTEM RESISTANCE TESTS

These tests will show the amount of voltage drop
across the generator output wire, from the generator
output (B+) terminal to the battery positive post.
They will also show the amount of voltage drop from
the ground (-) terminal on the generator to the bat-
tery negative post. A typical generator wiring har-
ness is shown in (Fig. 1). Wiring harness routing as
shown in (Fig. 1) may be slightly different depending
on vehicle model and/or engine. Refer to Group 8W,
Wiring Diagrams for additional information.
Fig. 1 Generator Terminals (Typical Wiring Harness
A voltmeter with a 0–18 volt DC scale should be
used for these tests. By repositioning the voltmeter
test leads, the point of high resistance (voltage drop)
can easily be found.
PREPARATION
(1) Before starting test, make sure battery is in
good condition and is fully-charged. See Group 8A,
Battery for more information.
Shown)
(2) Check condition of battery cables at battery.
Clean if necessary.
(3) Start the engine and allow it to reach normal
operating temperature.
(4) Shut engine off.
(5) Connect an engine tachometer.
(6) Fully engage the parking brake.
TEST
(1) Start engine.
(2) Place heater blower in high position.
(3) Turn on headlamps and place in high-beam
position.
(4) Turn vehicle interior lamps on.
(5) Bring engine speed up to 2400 rpm and hold.
(6) Testing (+) circuitry:
(a) Touch the negative lead of voltmeter directly
to battery positive post.
(b) Touch the positive lead of voltmeter to the
B+ output terminal stud on the generator (not the
terminal mounting nut). Voltage should be no
higher than 0.6 volts. If voltage is higher than 0.6
volts, touch test lead to terminal mounting stud
nut and then to the wiring connector. If voltage is
now below 0.6 volts, look for dirty, loose or poor
connection at this point. Also check condition of the
generator output wire-to-battery bullet connector
(if equipped). Refer to Group 8, Wiring for connec-
tor location. A voltage drop test may be performed
at each (+) connection in this circuit to locate the
excessive resistance.
(7) Testing (-) circuitry:
(a) Touch the negative lead of voltmeter directly
to battery negative post.
(b) Touch the positive lead of voltmeter to the
ground terminal stud on the generator case (not
the terminal mounting nut). Voltage should be no
higher than 0.3 volts. If voltage is higher than 0.3
volts, touch test lead to terminal mounting stud
nut and then to the wiring connector. If voltage is
now below 0.3 volts, look for dirty, loose or poor
connection at this point. A voltage drop test may be
performed at each (-) connection in this circuit to
locate the excessive resistance. This test can also
be performed between the generator case and the
engine. If test voltage is higher than 0.3 volts,
check for corrosion at generator mounting points or
loose generator mounting.

CURRENT OUTPUT TEST

The current output test will determine if the
charging system can deliver its minimum test cur-
rent (amperage) output. Refer to the Specifications
section at the end of this group for minimum test
current (amperage) requirements.
The first part of this test (Test 1) will determine
the combined amperage output of both the generator

CHARGING SYSTEM

8C - 3