Hummer H3. Manual — part 1133

Load Test

1. Disconnect the battery negative cable from the battery negative terminal. Refer to Battery

Negative Cable Disconnection and Connection.

2. Install the male end of the J 38758 to the battery ground terminal. See Special Tools.

3. Turn the J 38758 knob to the OFF position. See Special Tools.

4. Install the battery negative cable to the female end of the J 38758 . See Special Tools.

5. Turn the J 38758 knob to the ON position. See Special Tools.

6. Road test the vehicle and activate ALL of the accessories, including the radio and air

conditioning. This may take up to 30 minutes.

7. Park the vehicle. Turn the ignition switch to the OFF position and remove the ignition

switch key.

8. Connect a 10A fused jumper wire to the test switch tool terminals.

250 mA

3.3

500 mA

1.65

750 mA

1

1 A

0.8

2 A

0.4

CAUTION: Refer to Battery Disconnect Caution .

NOTE:

Do not turn the parasitic draw test switch to the OFF position with
the engine running. Damage will occur to the vehicle's electrical
system.

NOTE:

The test switch must be in the ON position when removing the fuses
in order to maintain continuity in the electrical system. This avoids
damaging the digital multimeter due to accidental overloading,
such as a door being opened to change a fuse.

IMPORTANT: The switch knob on the J 38758 is marked ON and OFF. See

Special Tools. When the switch knob is in the ON position, the
circuit is closed and electrical current will pass through the
switch. When the switch knob is in the OFF position, the circuit is
open and electrical current will not pass through the switch.

2007 Hummer H3

2007 ENGINE Engine Electrical - H3

9. Turn the J 38758 knob to the OFF position. See Special Tools. The current now flows

through the jumper wire.

10. Wait 1 minute. If the fuse blows, install an inductive ammeter and go to step 19 .

11. Remove the fused jumper wire.

12. Set a digital multimeter to the 10A scale.

13. Connect the digital multimeter to the test switch tool terminals.

14. Turn the J 38758 knob to the OFF position. See Special Tools. The current flows now

through the digital multimeter.

15. Wait 1 minute. Check and record the current reading.

1. When there is a current reading of 2A or less, turn the J 38758 knob to the ON

position. See Special Tools. The electrical current will now pass through the switch.

2. Then switch the digital multimeter down to the 2A scale for a more accurate reading

when the J 38758 knob is turned OFF. See Special Tools.

16. Turn the J 38758 knob to the OFF position. See Special Tools. Wait up to 45 minutes for

most vehicles.

17. Check and record the current reading.

18. Note the battery reserve capacity, amp hour rating. Refer to Battery Usage.

1. Divide the reserve capacity by 4, amp hour rating by 2.4.

2. Compare this to the multimeter milliampere reading taken in the previous step. The

parasitic current drain should not exceed this number. Example: If a battery has a
reserve capacity of 100 minutes, (60 A/H) the current drain should not exceed 25 mA.

19. If excessive current drain is not found at this time and there are no other apparent causes,

complete the following:

1. Using the MIN/MAX function of the digital multimeter, monitor the parasitic drain

overnight or during the day. This will determine if something has been activated during
that time frame.

NOTE:

The test switch must be in the ON position when removing
the fuses in order to maintain continuity in the electrical
system. This avoids damaging the digital multimeter due
to accidental overloading, such as a door being opened to
change a fuse.

IMPORTANT: Removing fuses, relays and connectors to determine the

failure area may wake up modules. You must wait for

2007 Hummer H3

2007 ENGINE Engine Electrical - H3

2. When the vehicle has an unacceptable amount of parasitic current drain, remove each

fuse one at a time until the current drain falls to an acceptable level. This will indicate
which circuit is causing the drain. Refer to Power Distribution Schematics to
diagnose exactly which part of the suspect circuit is causing the parasitic drain. In
some cases a non-fused circuit or component, such as a relay, is the cause of excessive
parasitic current drain.

3. Repeat the parasitic current drain test procedure after any repair has been completed

to make sure that the parasitic current drain is at an acceptable level.

4. When the cause of the excessive current drain has been located and repaired, remove

the J 38758 . See Special Tools.

20. Connect the battery negative cable to the battery negative terminal.

BATTERY COMMON CAUSES OF MALFUNCTION

A battery is not designed to last forever. With proper care, however, the battery will provide
years of good service. If the battery tests good but still fails to perform well, the following are
some of the more common causes:

A vehicle accessory was left on overnight.

The driving speeds have been slow with frequent stops with many electrical accessories in
use, particularly air conditioning, headlights, wipers, heated rear window, cellular
telephone, etc.

The electrical load has exceeded the generator output, particularly with the addition of
aftermarket equipment.

Existing conditions in the charging system, including the following possibilities:

A slipping belt

A bad generator

The battery has not been properly maintained, including a loose battery hold down or
missing battery insulator if used.

There are mechanical conditions in the electrical system, such as a short or a pinched wire,
attributing to power failure. Refer to General Electrical Diagnosis .

Electrolyte Freezing

The freezing point of electrolyte depends on its specific gravity. A fully charged battery will not

these modules to go to sleep or use the sleep function
on the scan tool.

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2007 ENGINE Engine Electrical - H3

freeze until the ambient temperature gets below -54°C (-65°F). However, a battery with a low
state of charge may freeze at temperatures as high as -7°C (+20°F). Since freezing may ruin a
battery, the battery should be protected against freezing by keeping it properly charged. As long
as the green eye is visible in the hydrometer, the freezing point of the battery will be somewhere
below -32°C (-25°F).

Battery Protection During Vehicle Storage

Certain devices on the vehicle maintain a small continuous current drain on the battery. A battery
that is not used for an extended period of time will discharge. Eventually permanent damage will
result. Discharged batteries will also freeze in cold weather. Refer to Battery Inspection/Test
(Non-HP2).

In order to maintain a battery state of charge while storing the vehicle for more than 30 days:

1. Ensure that the green dot is visible in the built-in hydrometer.

2. Disconnect the battery ground to protect the battery from discharge by parasitic current

drains.

When the battery cannot be disconnected:

1. Maintain a high state of charge.

2. Establish a regular schedule for recharging the battery every 20-45 days.

A battery that has remained in a discharged state for a long period of time is difficult to recharge
or may be permanently damaged.

JUMP STARTING IN CASE OF EMERGENCY (NON HP2)

IMPORTANT: If a green dot is not visible in the hydrometer, charge the

battery. Refer to Battery Charging.

CAUTION: Refer to BATTERY DISCONNECT CAUTION .

CAUTION: Batteries produce explosive gases. Batteries contain

corrosive acid. Batteries supply levels of electrical current
high enough to cause burns. Therefore, in order to reduce the
risk of personal injury while working near a battery, observe

2007 Hummer H3

2007 ENGINE Engine Electrical - H3