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ELECTRICAL 8A - 1
ELECTRICAL
GROUP INDEX
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AUDIO SYSTEMS ....................... 8F
BATTERY/STARTER/GENERATOR SERVICE . . . 8B
BATTERY/STARTING/CHARGING SYSTEMS
DIAGNOSTICS ........................ 8A
CHIME WARNING/REMINDER SYSTEM ...... 8U
HORNS ............................... 8G
IGNITION SYSTEMS ..................... 8D
INSTRUMENT PANEL AND GAUGES ........ 8E
LAMPS ............................... 8L
OVERHEAD CONSOLE ................... 8C
POWER LOCKS ......................... 8P
POWER MIRRORS ...................... 8T
POWER WINDOWS ...................... 8S
POWER SEATS ......................... 8R
REAR WINDOW DEFOGGER .............. 8N
RESTRAINTS .......................... 8M
TURN SIGNALS AND HAZARD WARNING FLASHER
...................................... 8J
VEHICLE SPEED CONTROL SYSTEM ........ 8H
VEHICLE THEFT SECURITY SYSTEM ....... 8Q
WINDSHIELD WIPERS AND WASHERS ...... 8K
WIRING DIAGRAMS .................... 8W
BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS
CONTENTS
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BATTERY TEST PROCEDURES ..............
ENGINE STARTER MOTOR TEST
PROCEDURES ........................
GENERATOR TEST PROCEDURES ON
VEHICLE .............................
IGNITION OFF DRAW (IOD) ................
SPECIFICATIONS .......................
GENERAL INFORMATION
The Battery, Starting, and Charging Systems oper-
ate with one another, and therefore, must be thor-
oughly tested as a complete system. In order for the
vehicle to start and charge properly, it must have a
battery that will perform to specifications. The starter
motor, generator, wiring, and electronics also must
perform within specifications. Group 8A covers Start-
ing (Fig. 1) and Charging (Fig. 2) System diagnostic
procedures. These procedures include the most basic
conventional methods to On-Board Diagnostics (OBD)
built into the Powertrain Control Module (PCM). Use
of an ammeter, volt/ohmmeter, battery charger, car-
bon pile rheostat (load tester), and 12 volt test light
will be required.
All OBD sensing systems are monitored by the
PCM. The PCM will store in memory any detectable
failure in the monitored circuits. Refer to Using On-
Board Diagnostic System in this group for more infor-
mation.
Fig. 1 Starting System Components (Typical)
8A - 2 BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS
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Fig. 2 Charging System Components
BATTERY TEST PROCEDURES
INDEX
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Abnormal Battery Discharging ...............
Battery Charging .........................
Battery Diagnostics Chart ...................
Battery Load Test .........................
Battery Open Circuit Voltage Test ..............
Battery Testing General Information ............
Causes of Battery Discharging ................
General Information .......................
Hydrometer Test .........................
State of Charge Test Using Test Indicator ........
Test Indicator ............................
GENERAL INFORMATION
The battery stores, stabilizes, and produces electri-
cal current. A battery must be able to accept a charge
and produce high-amperage current over an extended
period. A chemical reaction takes place between sulfu-
ric acid solution (electrolyte) and lead+/-plates in each
cell of the battery. As the battery discharges, the
plates collect acid from the electrolyte. When the
charging system charges the battery, water is con-
verted to sulfuric acid in the battery. The amount of
acid (specific gravity) in the electrolyte can be mea-
sured with a hydrometer. A factory installed battery
has a built-in test indicator to help determine state-
of-charge. Specific gravity can also be measured with
a hand held hydrometer. The battery is vented to
release gases that are created when the battery is
being charged. The battery top, posts, and terminals
should be cleaned when other underhood mainte-
nance is performed (Fig. 3).
WARNING: DO NOT ATTEMPT TO ASSIST BOOST,
CHARGE, OR TEST BATTERY WHEN ELECTROLYTE
LEVEL IS BELOW THE TOP OF THE PLATES (YEL-
LOW OR BRIGHT COLOR IS VISIBLE). PERSONAL
INJURY MAY OCCUR.
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BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS
8A - 3
TEST INDICATOR
A test indicator (hydrometer) built into the top of
battery case, provides visual information for battery
testing (Fig. 4). It is important when using test indi-
cator that the battery be level and have a clean top to
see correct indications. A light may be required to
view indicator.
WARNING: DO NOT USE OPEN FLAME. EXPLOSIVE
GASES FORM ABOVE BATTERY.
Fig. 3 Battery Construction and Test Indicator
When electrolyte level is below top of the plates
(yellow or bright indicator), distilled water should be
added. The battery must be completely charged
(green indicator) and the top, posts, and terminals
should be properly cleaned before diagnostic proce-
dures are performed. Refer to Group 8B -
Battery/Starter Service, for additional information.
All batteries are protected from high underhood
temperatures by a thermal shield. Always install
shield after removing the battery.
Fig. 4 Built in Test Indicator
STATE OF CHARGE TEST USING TEST INDICATOR
The built-in test indicator (hydrometer) measures
the specific gravity of the electrolyte. Specific gravity
(SG) will indicate state-of-charge (voltage); although,
the test indicator will not indicate cranking capacity
of the battery. Refer to Battery Load Test for more
information. Look into the sight glass and note the
color of the indicator (Fig. 5), refer to the following
description as color indicates:
GREEN
—75 to 100% state-of-charge
The battery is adequately charged for further test-
ing or return to use. If the vehicle will not crank for a
maximum 15 seconds, refer to Battery Load Test for
more information.
BLACK OR DARK
—0 to 75% state-of-charge
The battery is inadequately charged and must be
charged until green indicator is visible (12.4 volts or
more) before the battery is tested or returned to use.
Refer to Causes of Battery Discharging for more in-
formation.
YELLOW OR BRIGHT COLOR
BATTERY TESTING GENERAL INFORMATION
Before testing a battery, clean the top of the
battery case, posts and cable terminals.
Specific gravity is a ratio of the density of the
electrolyte and the density of pure water. The electro-
lyte is composed of sulfuric acid and water. Acid
makes up approximately 35% by weight or 24% by
volume.
The condition of a battery may be determined from
the results of 3 tests:
²
state of charge, using test indicator
²
hydrometer test
ability to supply current (battery load test).
Use test indicator first. If battery condition is not
certain then perform the Hydrometer test. If the spe-
cific gravity is less than 1.225, (with battery at room
temperature) the battery must be charged before pro-
ceeding with further testing. A battery that will not
accept a charge is defective and further testing is not
necessary.
Completely discharged batteries may take sev-
eral hours to accept a charge. See Charging A
Completely Discharged Battery.
A battery that has been fully charged but does not
pass the battery load test is defective.
A battery is fully charged when:
WARNING: DO NOT ATTEMPT TO CHARGE, TEST,
OR ASSIST BOOST BATTERY WHEN YELLOW OR
BRIGHT COLOR IS VISIBLE. PERSONAL INJURY
MAY OCCUR.
A yellow or bright color indicates electrolyte level in
the battery is below test indicator (Fig. 5). Water can
be added to a low maintenance battery. A low electro-
lyte level may be caused by an over charging condi-
tion. Refer to Generator Test Procedures On Vehicle
in this group.
²
all cells are gassing freely during charging
3 corrected specific gravity tests, taken at 1-hour
intervals, indicate no increase in specific gravity.
²
²
 8A - 4 BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS
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Fig. 5 Test Indicator Sight Glass
The fully charged battery should have a tempera-
ture corrected specific gravity of 1.260 to 1.290
If the specific gravity of all cells is above 1.235, but
variation between cells is more than 50 points (0.050),
it is a sign that the battery should be replaced.
If the specific gravity of one or more cells is less
than 1.235, recharge the battery at a rate of approxi-
mately 5 amperes. Continue charging until 3 consecu-
tive specific gravity tests, taken at one-hour intervals,
are constant.
If the cell specific gravity variation is more than 50
points (0.050) at the end of the charge period, replace
the battery.
When the specific gravity of all cells is above 1.235
and variation between cells is less than 50 points
(0.050), the battery may be tested under heavy load.
HYDROMETER TEST
Before performing a hydrometer test, remove
the battery caps and check the electrolyte level.
Add distilled water as required.
Before testing, visually inspect the battery for dam-
age (cracked case or cover, loose post, etc.) that would
cause the battery to be defective. To use the hydrom-
eter correctly, hold it with the top surface of the
electrolyte at eye level. Refer to manufacturers in-
structions for correct use of hydrometer.
Remove only enough electrolyte from the battery to
keep the float off the bottom of the hydrometer barrel
with pressure on the bulb released. Exercise care
when inserting the tip of the hydrometer into a cell to
avoid damage to the separators. Damaged separators
can cause premature battery failure.
Hydrometer floats are generally calibrated to indi-
cate the specific gravity correctly only at one fixed
temperature, 80°F (26.6°C). When testing the specific
gravity at any other temperature, a correction factor
is required.
The correction factor is approximately a specific
gravity value of 0.004, referred to as 4 points of
specific gravity. For each 10°F above 80°F (5.5°C
above 26.6°C), add 4 points. For each 10°F below 80°F
(5.5°C below 26.6°C), subtract 4 points. Always cor-
rect the specific gravity for temperature variation.
Test the specific gravity of the electrolyte in each
battery cell.
Example: A battery is tested at 10°F (-12.2°C) and
has a specific gravity of 1.240. Determine the actual
specific gravity as follows:
²
CAUSES OF BATTERY DISCHARGING
It is normal to havea5to20milliamperes Ignition
Off Draw (IOD) from the battery with all lamps OFF.
Electronic features or accessories that have a memory
circuit cause IOD. When a vehicle is not used for 20
days or more, remove IOD fuse in the Power Distribu-
tion Center to reduce battery discharging.
ABNORMAL BATTERY DISCHARGING
(1) Corroded battery posts and terminals.
(2) Loose or worn generator drive belt.
(3) Electrical loads that exceed the output of the
charging system due to equipment or accessories in-
stalled after delivery.
(4) Slow driving speeds (heavy traffic conditions) or
prolonged idling with high-amperage draw systems in
use.
(5) Defective circuit or component causing excess
IOD. Refer to Ignition Off Draw in this Group.
(6) Defective charging system.
(7) Defective battery.
Determine the number of degrees above or below
80°F.
80°F - 10°F = 70°F
BATTERY OPEN CIRCUIT VOLTAGE TEST
A battery voltage (no load) test will show state of
charge of a battery that will pass the Battery Load
Test described in this section.
Before proceeding
with this test or Battery Load Test, completely
charge battery as described in Battery Charg-
ing in this section.
If a battery has a no load voltage reading of 12.4
volts or greater and will not endure a load test, it is
defective and should be replaced. Refer to Group 8B -
Battery/Starter Service for instructions. To test bat-
tery no load voltage, perform the following operation:
(1) Before measuring open circuit voltage, the sur-
face charge must be removed from plates. Turn head
lights on for 15 seconds then allow up to 5 minutes
for voltage to stablize.
(2) Remove both battery cables, negative first.
²
Divide the result above by 10.
70°F/10 = 7
Multiply the result from the previous step by the
temperature correction factor (0.004).
7 x 0.004 = 0.028
The temperature at testing was below 80°F, there-
fore the temperature correction is subtracted.
1.240 - 0.028 = 1.212
The corrected specific gravity is 1.212.
²
²
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BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS
8A - 5
(3) Using a voltmeter connected to the battery
posts, see instructions provided with voltmeter, mea-
sure open circuit voltage (Fig. 6).
This voltage reading will indicate state of charge,
but will not reveal cranking capacity. Refer to Battery
Open Circuit Voltage chart.
BATTERY OPEN CIRCUIT VOLTAGE
Fig. 7 Volt-Amps-Load Tester (Typical)
Fig. 8 Volt-Ammeter-Load Tester Connections
Fig. 6 Testing Open Circuit Voltage
(3) Rotate the load control knob (carbon pile rheo-
stat) to apply a 300 amp load for 15 seconds then
return the control knob to off (Fig. 9). This will re-
move the surface charge from the battery.
BATTERY LOAD TEST
WARNING: IF BATTERY SHOWS SIGNS OF FREEZ-
ING, LEAKING, LOOSE POSTS, OR LOW ELECTRO-
LYTE LEVEL, DO NOT TEST. ACID BURNS OR EX-
PLOSIVE CONDITION MAY RESULT.
A battery load test will verify the cranking ability
based on the cold crank rating of the battery.
Before performing battery load test, the bat-
tery must be FULLY CHARGED.
(1) Remove both battery cables, negative first. Bat-
tery top and posts should be clean. If indicator is not
green, charge the battery. See Battery Charging Pro-
cedures in this section.
(2) Connect a suitable Volt-Ammeter-Load tester
(Fig. 7) to the battery posts (Fig. 8). Refer to operat-
ing instructions provided with the tester being used.
Check the open circuit voltage (no load) of the battery.
Voltage should be equal to or greater than 12.4 volts
(Fig. 7) with a green test indicator.
Fig. 9 Remove Surface Charge from Battery
(4) Allow the battery to stabilize to open circuit
voltage (may take up to 5 minutes).
(5) Rotate the load control knob to maintain a load
(50% of cold crank rating—see Specifications) for a
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