Jeep XJ. Manual - part 83

LOAD TEST

A battery load test will verify the battery cranking

capacity. The test is based on the Cold Cranking
Amperage (CCA) rating of the battery. See the label
affixed to the battery case, or refer to Battery in the
index of this service manual for the location of the
proper

factory-installed

battery

specifications

determine the battery CCA rating.

WARNING:

•

IF THE BATTERY SHOWS SIGNS OF FREEZ-

ING, LEAKING, LOOSE POSTS, OR LOW ELECTRO-
LYTE LEVEL, DO NOT TEST, ASSIST-BOOST, OR
CHARGE. THE BATTERY MAY ARC INTERNALLY
AND EXPLODE. PERSONAL INJURY AND/OR VEHI-
CLE DAMAGE MAY RESULT.

•

EXPLOSIVE HYDROGEN GAS FORMS IN AND

AROUND THE BATTERY. DO NOT SMOKE, USE
FLAME, OR CREATE SPARKS NEAR THE BATTERY.
PERSONAL INJURY AND/OR VEHICLE DAMAGE
MAY RESULT.

•

THE BATTERY CONTAINS SULFURIC ACID,

WHICH IS POISONOUS AND CAUSTIC. AVOID CON-
TACT WITH THE SKIN, EYES, OR CLOTHING. IN
THE EVENT OF CONTACT, FLUSH WITH WATER
AND CALL A PHYSICIAN IMMEDIATELY. KEEP OUT
OF THE REACH OF CHILDREN.

•

IF THE BATTERY IS EQUIPPED WITH REMOV-

ABLE CELL CAPS, BE CERTAIN THAT EACH OF
THE CELL CAPS IS IN PLACE AND TIGHT BEFORE
THE BATTERY IS RETURNED TO SERVICE. PER-
SONAL INJURY AND/OR VEHICLE DAMAGE MAY
RESULT FROM LOOSE OR MISSING CELL CAPS.

Before proceeding with this test, completely charge

the battery. Refer to Battery Charging in the index
of this service manual for the location of the proper
battery charging procedures.

(1) Disconnect and isolate both battery cables, neg-

ative cable first. The battery top and posts should be
clean.

(2) Connect a suitable volt-ammeter-load tester

(Fig. 10) to the battery posts (Fig. 11). See the
instructions provided by the manufacturer of the
tester you are using. Check the open-circuit voltage
(no load) of the battery. Refer to Open-Circuit Volt-

age Test in this section for the proper battery open-
circuit voltage test procedures. The battery open-
circuit voltage must be 12.4 volts or greater.

(3) Rotate the load control knob (carbon pile rheo-

stat) to apply a 300 ampere load to the battery for
fifteen seconds, then return the control knob to the
Off position (Fig. 12). This will remove the surface
charge from the battery.

(4) Allow the battery to stabilize to open-circuit

voltage. It may take up to five minutes for the bat-
tery voltage to stabilize.

(5) Rotate the load control knob to maintain a load

equal to 50% of the CCA rating of the battery (Fig.
13). After fifteen seconds, record the loaded voltage
reading, then return the load control knob to the Off
position.

(6) The voltage drop will vary with the battery

temperature at the time of the load test. The battery
temperature can be estimated by using the ambient
temperature during the past several hours. If the

Open Circuit Voltage

Open Circuit Volts

Charge Percentage

11.7 volts or less

12.0 volts

25%

12.2 volts

50%

12.4 volts

75%

12.6 volts or more

100%

Fig. 10 Volt-Ammeter-Load Tester - Typical

Fig. 11 Volt-Ammeter-Load Tester Connections -

Typical

1 – INDUCTION AMMETER CLAMP
2 – NEGATIVE CLAMP
3 – POSITIVE CLAMP

8A - 12

BATTERY

DIAGNOSIS AND TESTING (Continued)

battery has been charged, boosted, or loaded a few
minutes prior to the test, the battery will be some-
what warmer. See the Load Test Temperature chart
for the proper loaded voltage reading.

(7) If the voltmeter reading falls below 9.6 volts, at

a minimum battery temperature of 21° C (70° F), the
battery is faulty and must be replaced.

IGNITION-OFF DRAW TEST

The term Ignition-Off Draw (IOD) identifies a nor-

mal condition where power is being drained from the
battery with the ignition switch in the Off position. A
normal vehicle electrical system will draw from five
to twenty-five milliamperes (0.005 to 0.025 ampere)
with the ignition switch in the Off position, and all

non-ignition controlled circuits in proper working
order. The twenty-five milliamperes are needed to
enable the memory functions for the Powertrain Con-
trol Module (PCM), digital clock, electronically tuned
radio, and other modules which may vary with the
vehicle equipment.

A vehicle that has not been operated for approxi-

mately twenty days, may discharge the battery to an
inadequate level. When a vehicle will not be used for
twenty days or more (stored), remove the IOD fuse
from the Power Distribution Center (PDC). This will
reduce battery discharging.

Excessive IOD can be caused by:
• Electrical items left on.

• Faulty or improperly adjusted switches.

• Faulty or shorted electronic modules and compo-

nents.

• An internally shorted generator.

• Intermittent shorts in the wiring.
If the IOD is over twenty-five milliamperes, the

problem must be found and corrected before replac-
ing a battery. In most cases, the battery can be
charged and returned to service after the excessive
IOD condition has been corrected.

(1) Verify that all electrical accessories are off.

Turn off all lamps, remove the ignition key, and close
all doors. If the vehicle is equipped with an illumi-
nated entry system or an electronically tuned radio,
allow the electronic timer function of these systems
to automatically shut off (time out). This may take
up to three minutes. See the Electronic Module Igni-
tion-Off Draw table for more information.

Fig. 12 Remove Surface Charge from Battery -

Typical

Fig. 13 Load 50% CCA Rating - Note Voltage -

Typical

Load Test Temperature

Minimum Voltage

Temperature

°F

°C

9.6 volts

70° and above

21° and above

9.5 volts

60°

16°

9.4 volts

50°

10°

9.3 volts

40°

4°

9.1 volts

30°

-1°

8.9 volts

20°

-7°

8.7 volts

10°

-12°

8.5 volts

0°

-18°

BATTERY

8A - 13

DIAGNOSIS AND TESTING (Continued)

Electronic Module Ignition-Off Draw (IOD)

Module

Time Out?

(If Yes, Interval and Wake-Up Input)

IOD

IOD After Time

Out

Radio

1 to 3

milliamperes

N/A

Audio Power

Amplifier

up to 1

milliampere

N/A

Central Timer Module

(CTM)

4.75

milliamperes

N/A

Powertrain Control

Module (PCM)

0.95 milliampere

N/A

ElectroMechanical

Instrument Cluster

(EMIC)

0.44 milliampere

N/A

Combination Flasher

0.08 milliampere

N/A

(2) Determine that the under-hood lamp is operat-

ing properly, then disconnect the lamp wire harness
connector or remove the lamp bulb.

(3) Disconnect the battery negative cable.
(4) Set an electronic digital multi-meter to its

highest amperage scale. Connect the multi-meter
between the disconnected battery negative cable ter-
minal clamp and the battery negative terminal post.
Make sure that the doors remain closed so that the
illuminated entry system is not activated. The multi-
meter amperage reading may remain high for up to
three minutes, or may not give any reading at all
while set in the highest amperage scale, depending
upon the electrical equipment in the vehicle. The
multi-meter leads must be securely clamped to the
battery negative cable terminal clamp and the bat-
tery negative terminal post. If continuity between the
battery negative terminal post and the negative cable
terminal clamp is lost during any part of the IOD
test, the electronic timer function will be activated
and all of the tests will have to be repeated.

(5) After about three minutes, the high-amperage

IOD reading on the multi-meter should become very
low or nonexistent, depending upon the electrical
equipment in the vehicle. If the amperage reading
remains high, remove and replace each fuse or circuit
breaker in the Power Distribution Center (PDC) and
then in the Junction Block (JB) one at a time (refer
to Power Distribution Center and Junction
Block in the index of this service manual for the
location of complete PDC and JB fuse and circuit
breaker identification contained in the wiring dia-
grams) until the amperage reading becomes very low,
or nonexistent. This will isolate each circuit and
identify the circuit that is the source of the high-am-
perage IOD. If the amperage reading remains high
after removing and replacing each fuse and circuit

breaker, disconnect the wire harness from the gener-
ator. If the amperage reading now becomes very low
or nonexistent, refer to Charging System in the
index of this service manual for the location of the
proper charging system diagnosis and testing proce-
dures. After the high-amperage IOD has been cor-
rected, switch the multi-meter to progressively lower
amperage scales and, if necessary, repeat the fuse
and circuit breaker remove-and-replace process to
identify and correct all sources of excessive IOD. It is
now safe to select the lowest milliampere scale of the
multi-meter to check the low-amperage IOD.

CAUTION: Do not open any doors, or turn on any
electrical accessories with the lowest milliampere
scale selected, or the multi-meter may be damaged.

(6) Observe the multi-meter reading. The low-am-

perage IOD should not exceed twenty-five milliam-
peres (0.025 ampere). If the current draw exceeds
twenty-five milliamperes, isolate each circuit using
the fuse and circuit breaker remove-and-replace pro-
cess in Step 5. The multi-meter reading will drop to
within the acceptable limit when the source of the
excessive current draw is disconnected. Repair this
circuit as required; whether a wiring short, incorrect
switch adjustment, or a component failure is at fault.

BATTERY CABLES

DIAGNOSIS

A voltage drop test will determine if there is exces-

sive resistance in the battery cable terminal connec-
tions or the battery cables. If excessive resistance is
found in the battery cable connections, the connec-
tion point should be disassembled, cleaned of all cor-
rosion

foreign

material,

then

reassembled.

Following reassembly, check the voltage drop for the

8A - 14

BATTERY

DIAGNOSIS AND TESTING (Continued)

battery cable connection and the battery cable again
to confirm repair.

When performing the voltage drop test, it is impor-

tant to remember that the voltage drop is giving an
indication of the resistance between the two points at
which the voltmeter probes are attached. EXAM-
PLE: When testing the resistance of the battery pos-
itive cable, touch the voltmeter leads to the battery
positive cable terminal clamp and to the battery pos-
itive cable eyelet terminal at the starter solenoid
B(+) terminal stud. If you probe the battery positive
terminal post and the battery positive cable eyelet
terminal at the starter solenoid B(+) terminal stud,
you are reading the combined voltage drop in the
battery positive cable terminal clamp-to-terminal
post connection and the battery positive cable.

TESTING

VOLTAGE DROP TEST

WARNING:

•

IF THE BATTERY SHOWS SIGNS OF FREEZ-

ING, LEAKING, LOOSE POSTS, OR LOW ELECTRO-
LYTE LEVEL, DO NOT TEST, ASSIST-BOOST, OR
CHARGE. THE BATTERY MAY ARC INTERNALLY
AND EXPLODE. PERSONAL INJURY AND/OR VEHI-
CLE DAMAGE MAY RESULT.

•

EXPLOSIVE HYDROGEN GAS FORMS IN AND

AROUND THE BATTERY. DO NOT SMOKE, USE
FLAME, OR CREATE SPARKS NEAR THE BATTERY.
PERSONAL INJURY AND/OR VEHICLE DAMAGE
MAY RESULT.

•

THE BATTERY CONTAINS SULFURIC ACID,

WHICH IS POISONOUS AND CAUSTIC. AVOID CON-
TACT WITH THE SKIN, EYES, OR CLOTHING. IN
THE EVENT OF CONTACT, FLUSH WITH WATER
AND CALL A PHYSICIAN IMMEDIATELY. KEEP OUT
OF THE REACH OF CHILDREN.

•

IF THE BATTERY IS EQUIPPED WITH REMOV-

The following operation will require a voltmeter

accurate to 1/10 (0.10) volt. Before performing this
test, be certain that the following procedures are
accomplished:

• The battery is fully-charged and load tested.

Refer to Battery Charging in the index of this ser-
vice manual for the location of the proper battery
charging procedures. Refer to Battery in the index of
this service manual for the location of the battery
diagnosis

and

testing

procedures,

including

the

proper battery load test procedures.

• Fully engage the parking brake.

• If the vehicle is equipped with an automatic

transmission, place the gearshift selector lever in the
Park position. If the vehicle is equipped with a man-
ual transmission, place the gearshift selector lever in
the Neutral position and block the clutch pedal in the
fully depressed position.

• Verify that all lamps and accessories are turned

off.

• To prevent the engine from starting, remove the

Automatic ShutDown (ASD) relay. The ASD relay is
located in the Power Distribution Center (PDC), in
the engine compartment. See the fuse and relay lay-
out label affixed to the underside of the PDC cover
for ASD relay identification and location.

(1) Connect the positive lead of the voltmeter to

the battery negative terminal post. Connect the neg-
ative lead of the voltmeter to the battery negative
cable terminal clamp (Fig. 14). Rotate and hold the
ignition switch in the Start position. Observe the
voltmeter. If voltage is detected, correct the poor con-
nection between the battery negative cable terminal
clamp and the battery negative terminal post.

(2) Connect the positive lead of the voltmeter to

the battery positive terminal post. Connect the nega-
tive lead of the voltmeter to the battery positive cable
terminal clamp (Fig. 15). Rotate and hold the ignition
switch in the Start position. Observe the voltmeter. If
voltage is detected, correct the poor connection
between the battery positive cable terminal clamp
and the battery positive terminal post.

(3) Connect the voltmeter to measure between the

battery positive cable terminal clamp and the starter
solenoid B(+) terminal stud (Fig. 16). Rotate and hold
the ignition switch in the Start position. Observe the

Fig. 14 Test Battery Negative Connection

Resistance - Typical

1 – VOLTMETER
2 – BATTERY

BATTERY

8A - 15

DIAGNOSIS AND TESTING (Continued)

Content .. 81 82 83 84 ..