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ELECTRICAL

8A - 1

ELECTRICAL

GROUP INDEX

Group

AUDIO SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . .

BATTERY/STARTER/GENERATOR SERVICE . . . .

BATTERY/STARTING/CHARGING SYSTEMS

DIAGNOSTICS . . . . . . . . . . . . . . . . . . . . . . . . .

CHIME/BUZZER WARNING SYSTEMS . . . . . . . .

HORNS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

IGNITION SYSTEMS . . . . . . . . . . . . . . . . . . . . . .

INSTRUMENT PANEL AND GAUGES . . . . . . . . .

LAMPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

OVERHEAD CONSOLE . . . . . . . . . . . . . . . . . . . .

POWER LOCKS . . . . . . . . . . . . . . . . . . . . . . . . . .

POWER MIRRORS . . . . . . . . . . . . . . . . . . . . . . .

POWER SEATS . . . . . . . . . . . . . . . . . . . . . . . . . . 8R

POWER WINDOWS . . . . . . . . . . . . . . . . . . . . . . . 8S

REAR WINDOW DEFOGGER . . . . . . . . . . . . . . . 8N

RESTRAINT SYSTEMS . . . . . . . . . . . . . . . . . . . 8M

TURN SIGNAL AND HAZARD WARNING

SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8J

VEHICLE SPEED CONTROL SYSTEM . . . . . . . . . 8H

WIPER AND WASHER SYSTEMS . . . . . . . . . . . . 8K

XJ WIRING DIAGRAMS-LEFT HAND DRIVE . . . 8W

XJ WIRING DIAGRAMS-RIGHT HAND DRIVE . 8W

YJ WIRING DIAGRAMS . . . . . . . . . . . . . . . . . . 8W

BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS

CONTENTS

page

BATTERY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

CHARGING SYSTEM . . . . . . . . . . . . . . . . . . . . . 17

IGNITION-OFF DRAW . . . . . . . . . . . . . . . . . . . . 10

GENERAL INFORMATION

The battery, starting, and charging systems operate

with one another; therefore, they must be tested as a

complete system. In order for the vehicle to start and

charge properly, all of the components involved in

these systems must perform within specifications.

Group 8A covers battery, starting (Fig. 1) and

charging (Fig. 2) system diagnostic procedures. These

procedures include the most basic conventional diag-

nostic methods, to On-Board Diagnostics (OBD) built

SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . 23

STARTING SYSTEM . . . . . . . . . . . . . . . . . . . . . . 11

USING ON-BOARD DIAGNOSTIC SYSTEM . . . . 22

into the Powertrain Control Module (PCM). Use of an

induction milliamp ammeter, volt/ohmmeter, battery

charger, carbon pile rheostat (load tester), and 12-

volt test lamp will be required.

All OBD-sensed systems are monitored by the

PCM. Each monitored circuit is assigned a Diagnos-

tic Trouble Code (DTC). The PCM will store a DTC in

electronic memory for any failure it detects. See Us-

ing On-Board Diagnostic System in this group for

more information.

8A - 2

BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS

Fig. 1 Starting System Components (Typical)

Fig. 2 Charging System Components (Typical)

BATTERY

GENERAL INFORMATION

The storage battery is a device used to store elec-

trical energy potential in a chemical form. When an

electrical load is applied to the battery terminals, an

electrochemical reaction occurs within the battery.

This reaction causes the battery to discharge electri-

cal current.

The battery is made up of 6 individual cells that

are connected in series. Each cell contains positively

charged plate groups made of lead oxide, and nega-

tively charged plate groups made of sponge lead.

These dissimilar metal plates are submerged in a

sulfuric acid and water solution called electrolyte.

As the battery discharges, a gradual chemical

change takes place within each cell. The sulfuric acid

in the electrolyte combines with the plate materials,

causing both plates to change to lead sulfate. At the

same time, oxygen from the positive plate material

combines with hydrogen from the sulfuric acid, caus-

ing the electrolyte to become mainly water.

The chemical changes within the battery are

caused by movement of excess or free electrons be-

tween the positive and negative plate groups. This

movement of electrons produces a flow of electrical

current through the load device attached to the bat-

tery terminals.

As the plate materials become more similar chem-

ically, and the electrolyte becomes less acid, the volt-

age potential of each cell is reduced. However, by

charging the battery with a voltage higher than that

of the battery, the process is reversed.

Charging the battery gradually changes the sul-

fated lead plates back into sponge lead and lead ox-

ide, and the water back into sulfuric acid. This action

restores the difference in electron charges deposited

on the plates, and the voltage potential of the battery

cells.

For a battery to remain useful, it must be able to

produce high-amperage current over an extended pe-

riod. A battery must also be able to accept a charge,

so that its voltage potential may be restored.

In addition to producing and storing electrical en-

ergy, the battery serves as a capacitor or voltage sta-

bilizer for the vehicle electrical system. It absorbs

abnormal or transient voltages caused by switching

of any of the vehicle’s electrical components.

The battery is vented to release excess gas that is

created when the battery is being charged or dis-

BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS

8A - 3

charged. However, even with these vents, hydrogen

gas can collect in or around the battery. If hydrogen

gas is exposed to flame or sparks, it can ignite.

If the electrolyte level is low, the battery could arc

internally and explode. If the battery is equipped

with removable cell caps, add distilled water when-

ever the electrolyte level is below the top of the

plates. If the battery cell caps cannot be removed, the

battery must be replaced when the electrolyte level is

low.

WARNING: DO NOT ATTEMPT TO ASSIST BOOST,

CHARGE, OR TEST BATTERY WHEN ELECTRO-

LYTE LEVEL IS BELOW THE TOP OF THE PLATES.

PERSONAL INJURY MAY OCCUR.

BATTERY RATINGS

Currently, there are 2 commonly accepted methods

for rating and comparing battery performance. These

ratings are called Cold Cranking Amperage (CCA),

and Reserve Capacity (RC). Be certain that a replace-

ment battery has CCA and RC ratings that equal or

exceed the original equipment specification for the

vehicle being serviced. See Battery Classifications

and Ratings charts in Specifications at the back of

this group.

COLD CRANKING AMPERAGE

The Cold Cranking Amperage (CCA) rating speci-

fies how much current (in amperes) the battery can

deliver for 30 seconds at -17.7°C (0°F). Terminal volt-

age must not fall below 7.2 volts during or after the

30 second discharge. The CCA required is generally

higher as engine displacement increases, depending

also upon the starter current draw requirements.

RESERVE CAPACITY

The Reserve Capacity (RC) rating specifies the

time (in minutes) it takes for battery terminal volt-

age to fall below 10.2 volts at a discharge rate of 25

amps. RC is determined with the battery fully-

charged at 26.7°C (80°F). This rating estimates how

long the battery might last after a charging system

failure, under minimum electrical load.

(2)

Cranking Capacity

This can be determined

by performing a battery load test, which measures

the ability of the battery to supply high-amperage

current.

If the battery has a built-in test indicator, use this

test first. If it has no test indicator, but has remov-

able cell caps, perform the hydrometer test first. If

cell caps are not removable, or a hydrometer is not

available, perform the open circuit voltage test first.

The battery must be charged before proceeding

with a load test if:

•

the built-in test indicator has a black or dark color

visible

•

the temperature corrected specific gravity is less

than 1.235

•

the open circuit voltage is less than 12.4 volts.

A battery that will not accept a charge is faulty

and further testing is not required. A battery that is

fully-charged, but does not pass the load test is

faulty and must be replaced.

Completely discharged batteries may take

several hours to accept a charge. See Charging

Completely Discharged Battery.

A battery is fully-charged when:

•

all cells are gassing freely during charging

•

a green color is visible in the sight glass of the

built-in test indicator

•

three corrected specific gravity tests, taken at

1-hour intervals, indicate no increase in specific grav-

ity

•

open circuit voltage is 12.4 volts or greater.

DIAGNOSIS

The battery must be completely charged and the

top, posts, and terminal clamps should be properly

cleaned before diagnostic procedures are performed.

Refer to Group 8B - Battery/Starter/Generator Ser-

vice for more information.

The condition of a battery is determined by two cri-

teria:

(1)

State-Of-Charge

This can be determined by

viewing the built-in test indicator, by checking spe-

cific gravity of the electrolyte (hydrometer test), or by

checking battery voltage (open circuit voltage test).

ABNORMAL BATTERY DISCHARGING

Any of the following conditions can result in abnor-

mal 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, possibly due to equipment installed

after manufacture or repeated short trip use.

(4) Slow driving speeds (heavy traffic conditions) or

prolonged idling with high-amperage draw systems

in use.

(5) Faulty circuit or component causing excessive

ignition-off draw. See Ignition-Off Draw in this group

for diagnosis.

(6) Faulty charging system.

(7) Faulty or incorrect battery.

BUILT-IN TEST INDICATOR

A test indicator (hydrometer) built into the top of

the battery case, provides visual information for bat-

tery testing (Fig. 1). It is important when using the

test indicator that the battery be level and have a

clean sight glass to see correct indications. Additional

light may be required to view indicator.

8A - 4

BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS

BATTERY DIAGNOSIS

BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS

8A - 5

WARNING: DO NOT USE OPEN FLAME AS A

SOURCE OF ADDITIONAL LIGHT FOR VIEWING

TEST INDICATOR. EXPLOSIVE HYDROGEN GAS

MAY BE PRESENT IN THE AREA SURROUNDING

BATTERY.

Fig. 2 Built-In Test Indicator Sight Glass

HYDROMETER TEST

The hydrometer test reveals the battery state-of-

charge by measuring the specific gravity of the elec-

trolyte. This test cannot be performed on batteries

with non-removable cell caps. If battery has non-re-

movable cell caps, see Built-In Test Indicator or Open

Circuit Voltage Test.

Specific gravity is a comparison of the density of

the electrolyte to the density of pure water. Pure wa-

ter has a specific gravity of 1.000, and sulfuric acid

has a specific gravity of 1.835. Sulfuric acid makes

up approximately 35% of the electrolyte by weight, or

24% by volume.

In a fully-charged battery the electrolyte will have

a temperature corrected specific gravity of 1.260 to

1.290. However, a specific gravity of 1.235 or above is

satisfactory for battery load testing and/or return to

service.

Before testing, visually inspect battery for any

damage (cracked case or cover, loose posts, etc.) that

would cause the battery to be faulty. Then remove

cell caps and check electrolyte level. Add distilled wa-

ter if electrolyte level is below the top of the battery

plates.

To use the hydrometer correctly, hold it with the

top surface of the electrolyte at eye level. Refer to the

hydrometer manufacturer’s instructions for correct

use of hydrometer. Remove only enough electrolyte

from the battery so the float is off the bottom of the

hydrometer barrel with pressure on the bulb re-

leased.

Exercise care when inserting the tip of the hydrom-

eter into a cell to avoid damaging the plate separa-

tors. Damaged plate separators can cause premature

battery failure.

Hydrometer floats are generally calibrated to indi-

cate the specific gravity correctly only at 26.7°C

(80°F). 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 spe-

cific gravity. For each 5.5°C above 26.7°C (10°F above

80°F), add 4 points. For each 5.5°C below 26.7°C

(10°F below 80°F), subtract 4 points. Always correct

Fig. 1 Built-In Test Indicator

Like a hydrometer, the built-in test indicator mea-

sures the specific gravity of the electrolyte. Specific

gravity will indicate battery state-of-charge. How-

ever, the test indicator will not indicate cranking ca-

pacity of the battery. See Load Test in this group for

more information.

Look into the sight glass and note the color of the

indicator (Fig. 2). Refer to the following description,

as the color indicates:

GREEN—indicates

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 minimum of 15 seconds with a fully-charged bat-

tery, perform Load Test.

BLACK OR DARK—indicates

0% to 75% state-of-

charge.

The battery is inadequately charged and must be

charged until green indicator (Fig. 2) is visible in

sight glass (12.4 volts or more) before the battery is

tested further or returned to use. See Abnormal Bat-

tery Discharging in this group to diagnose cause of

discharged condition.

YELLOW OR BRIGHT—indicates

low electrolyte

level.

The electrolyte level in the battery is below test in-

dicator (Fig. 2). A maintenance-free battery with non-

removable cell caps must be replaced if electrolyte

level is low. Water can be added to a low-mainte-

nance battery with removable cell caps. A low electro-

lyte level may be caused by an over-charging

condition. See Charging System in this group to di-

agnose an over-charging condition.

WARNING: DO NOT ATTEMPT TO CHARGE, TEST,

OR ASSIST BOOST BATTERY WHEN YELLOW OR

BRIGHT COLOR IS VISIBLE IN SIGHT GLASS OF

TEST INDICATOR. LOW ELECTROLYTE LEVEL CAN

ALLOW BATTERY TO ARC INTERNALLY AND EX-

PLODE. PERSONAL INJURY MAY OCCUR.

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