Dodge Ram Truck 1500-2500-3500. Manual — part 324

OPEN-CIRCUIT VOLTAGE TEST

A battery open-circuit voltage (no load) test will show the approximate state-of-charge of a battery. This test can be
used in place of the hydrometer test when a hydrometer is not available, or for maintenance-free batteries with
non-removable cell caps.

Before proceeding with this test, completely charge the battery (Refer to 8 - ELECTRICAL/BATTERY SYSTEM/BAT-
TERY - STANDARD PROCEDURE - BATTERY CHARGING).

1. Before measuring the open-circuit voltage, the surface charge must be removed from the battery. Turn on the

headlamps for fifteen seconds, then allow up to five minutes for the battery voltage to stabilize.

2. Disconnect and isolate both battery cables, negative cable first.

3. Using a voltmeter connected to the battery posts measure the open-circuit voltage.

See the Open-Circuit Voltage Table. This voltage reading will indicate the battery state-of-charge, but will not reveal
its cranking capacity. If a battery has an open-circuit voltage reading of 12.4 volts or greater, it may be load tested
to reveal its cranking capacity (Refer to 8 - ELECTRICAL/BATTERY SYSTEM/BATTERY - STANDARD PROCE-
DURE - USING MICRO 420 BATTERY TESTER).

OPEN CIRCUIT VOLTAGE TABLE

Open Circuit Voltage

Charge Percentage

11.7 volts or less

0%

12.0 volts

25%

12.2 volts

50%

12.4 volts

75%

12.6 volts or more

100%

IGNITION-OFF DRAW TEST

The term Ignition-Off Draw (IOD) identifies a normal 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 thirty-five milliamperes
(0.005 to 0.035 ampere) with the ignition switch in the Off position, and all non-ignition controlled circuits in proper
working order. Up to thirty-five milliamperes are needed to enable the memory functions for the Powertrain Control
Module (PCM), digital clock, electronically tuned radio, and other modules which may vary with the vehicle equip-
ment.

A vehicle that has not been operated for approximately 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 Junction
Block (JB). This will reduce battery discharging.

Excessive IOD can be caused by:

•

Electrical items left on.

•

Inoperative or improperly adjusted switches.

•

Inoperative or shorted electronic modules and components.

•

An internally shorted generator.

•

Intermittent shorts in the wiring.

If the IOD is over thirty-five milliamperes, the problem must be found and corrected before replacing a battery. In
most cases, the battery can be charged and returned to service after the excessive IOD condition has been cor-
rected.

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 illuminated 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 Elec-
tronic Module Ignition-Off Draw Table for more information.

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BATTERY SYSTEM

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ELECTRONIC MODULE IGNITION-OFF DRAW (IOD) TABLE

Module

Time Out?

(If Yes, Interval And Wake-Up Input)

IOD

IOD After Time

Out

Radio

No

1 to 3

milliamperes

N/A

Audio Power

Amplifier

No

up to 1

milliampere

N/A

Central Timer Module

(CTM)

No

4.75

milliamperes

(max.)

N/A

Powertrain Control

Module (PCM)

No

0.95 milliampere

N/A

ElectroMechanical

Instrument Cluster

(EMIC)

No

0.44 milliampere

N/A

Combination Flasher

No

0.08 milliampere

N/A

2. Determine that the underhood lamp is operating 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 discon-

nected battery negative cable terminal 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 battery 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 elec-
tronic 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 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 until the amperage reading becomes very low, or nonexistent. Refer to the appropriate wiring
information for complete PDC and JB fuse, circuit breaker, and circuit identification. This will isolate each circuit
and identify the circuit that is the source of the high-amperage IOD. If the amperage reading remains high after
removing and replacing each fuse and circuit breaker, disconnect the wire harness from the generator. If the
amperage reading now becomes very low or nonexistent, diagnose and repair the Charging System as neces-
sary. After the high-amperage IOD has been corrected, 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-amperage IOD should not exceed thirty-five milliamperes (0.035

ampere). If the current draw exceeds thirty-five milliamperes, isolate each circuit using the fuse and circuit
breaker remove-and-replace process 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 an inoperative component is the cause.

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BATTERY SYSTEM

8F - 17

REMOVAL

1. Turn the ignition switch to the Off position. Be cer-

tain that all electrical accessories are turned off.

2. Loosen the battery negative cable terminal clamp

pinch-bolt hex nut.

3. Disconnect the battery negative cable terminal

clamp from the battery negative terminal post. If
necessary, use a battery terminal puller (2) to
remove the terminal clamp from the battery post.

4. Loosen the battery positive cable terminal clamp

pinch-bolt hex nut.

5. Disconnect the battery positive cable terminal

clamp from the battery positive terminal post. If
necessary, use a battery terminal puller (2) to remove the terminal clamp from the battery post.

6. Remove the battery hold down retaining bolt (6)

and battery hold down (5).

WARNING: WEAR A SUITABLE PAIR OF RUBBER
GLOVES (NOT THE HOUSEHOLD TYPE) WHEN
REMOVING

A

BATTERY

BY

HAND.

SAFETY

GLASSES SHOULD ALSO BE WORN. IF THE BAT-
TERY IS CRACKED OR LEAKING, THE ELECTRO-
LYTE CAN BURN THE SKIN AND EYES.

7. Remove the battery (2) from the battery tray.

INSTALLATION

1. Clean and inspect the battery (2), (Refer to 8 -

ELECTRICAL/BATTERY SYSTEM - CLEANING)
and (Refer to 8 - ELECTRICAL/BATTERY SYS-
TEM - INSPECTION) for the proper procedures.

CAUTION: Be certain that the battery cable termi-
nal clamps are connected to the correct battery
terminal posts. Reversed battery polarity may
damage electrical components of the vehicle.

2. Position the battery into the battery tray. Ensure

that the battery positive and negative terminal
posts are correctly positioned. The battery cable
terminal clamps must reach the correct battery ter-
minal post without stretching the cables.

3. Position the battery hold down (5) and install the

retaining bolt (6).

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BATTERY SYSTEM

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4. Clean the battery cable terminal clamps and the battery terminal posts, (Refer to 8 - ELECTRICAL/BATTERY

SYSTEM - CLEANING) for the proper procedures.

5. Reconnect the battery positive cable terminal clamp to the battery positive terminal post. Tighten the terminal

clamp pinch-bolt hex nut to 4 N·m (35 in. lbs.).

6. Reconnect the battery negative cable terminal clamp to the battery negative terminal post. Tighten the terminal

clamp pinch-bolt hex nut to 4 N·m (35 in. lbs.).

7. Apply a thin coating of petroleum jelly or chassis grease to the exposed surfaces of the battery cable terminal

clamps and the battery terminal posts.

8. Obtain an appropriate scan tool and check the PCM for any stored battery disconnect trouble codes. Clear codes

if required.

BATTERY HOLDDOWN

REMOVAL

CAUTION: Never operate a vehicle without a bat-
tery hold down device properly installed. Damage
to the vehicle, components and battery could
result.

1. Verify that the ignition switch and all accessories

are OFF.

2. Disconnect and isolate the battery negative cable.

3. Remove the bolt (6) from the battery hold down

bracket (5) and remove the bracket from the
vehicle.

INSTALLATION

1. Clean and inspect the battery hold down bracket

(5) and bolt (6) (Refer to 8 - ELECTRICAL/BAT-
TERY SYSTEM - CLEANING).

2. Position the battery hold down bracket in the bat-

tery tray.

CAUTION: Be certain that the hold down bracket is
properly positioned in the battery tray before tight-
ening the hold down bolt or damage to the battery
and tray may result.

3. Install and tighten the battery hold down retaining

bolt.

DR/DH

BATTERY SYSTEM

8F - 19