Jeep 1997 Grand Cherokee Service Manual page 310

8A - 10 BATTERY
DIAGNOSIS AND TESTING (Continued)
Fig. 9 Load 50% CCA Rating - Note Voltage- Typical
minutes prior to the test, the battery will be some-
what warmer. See the Load Test Temperature chart
for the proper loaded voltage reading.
Load Test Temperature
Minimum Voltage
9.6 volts 70° and above
9.5 volts
9.4 volts
9.3 volts
9.1 volts
8.9 volts
8.7 volts
8.5 volts
(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
Ignition-Off Draw (IOD) refers to power being
drained from the battery with the ignition switch in
the Off position. A normal vehicle electrical system
will draw from five to thirty milliamperes (0.005 to
0.030 ampere) with the ignition switch in the Off
position, and all non-ignition controlled circuits in
proper working order. The thirty milliamperes are
needed to enable the memory functions for the Pow-
ertrain Control Module (PCM), digital clock, electron-
ically 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
Temperature
°F °C
21° and above
60° 16°
50° 10°
40° 4°
30° -1°
20° -7°
10° -12°
0° -18°
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 thirty milliamperes, the problem
must be found and corrected before replacing a bat-
tery. In most cases, the battery can be charged and
returned to service after the excessive IOD has been
corrected.
DIAGNOSIS
(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 a illumi-
nated entry system or electronically tuned radio,
allow the electronic timer function of these systems
to automatically shut off (time out). This may take
up to three minutes.
(2) Determine that the underhood lamp is operat-
ing properly, then unplug the lamp wire harness con-
nector 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
clamp and the battery negative terminal post. Make
sure that the doors remain closed so that the illumi-
nated 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 on the vehicle. The multi-meter
leads must be securely clamped to the battery nega-
tive cable clamp and the battery negative terminal
post. If continuity between the battery negative ter-
minal post and the negative cable clamp is lost dur-
ing 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 non-existent, depending upon the electrical
equipment on the vehicle. If the amperage reading
remains high, remove each fuse or circuit breaker
(refer to Group 8W - Wiring Diagrams for more infor-
mation) until the amperage reading becomes very
low, or non-existent. This will isolate each circuit and
identify the source of the high-amperage IOD. If the
amperage reading remains high after disconnecting
each fuse and circuit breaker, unplug the wire har-
ness connector from the generator. If the amperage
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