Hummer H1 (2006+). Manual - part 336

12-20

Electrical System

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Exterior Fuse Box

Figure 12-20: Exterior Fuse Box

The exterior fuse box is located under the hood on the driver’s side of the engine compartment. The exterior fuse box houses mini
and maxi fuses, circuit breakers, and relays which supply power to many of the electrical components in the engine compartment.
The exterior fuse box can be accessed by first removing the left side cowl cover then removing the fuse box cover itself. Fuse and
relay locations are labeled on the inside of the cover. Spare mini fuses are located in the exterior fuse box for convient replacement.
A fuse puller is also provided to ease fuse removal.

MINI-FUSE

BLANK

MAXI-FUSES

LAYOUT

EXTERIOR

FUSE BOX

FUSE

PULLER

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Electrical System 12-21

Mini-Fuse Identification (Exterior Fuse Box)

Maxi-Fuse Identification (Exterior Fuse Box)

Auxiliary Power Studs

The external fuse box provides 2 threaded studs for use as auxiliary power connections. Each stud is fused for up to 30 amps with
maxi-fuses located in the external fuse box. Both studs provide battery power.

Fuse

Amperage

Circuit Protected

–

Blank

–

Blank

Heated Windshield

–

Blank

ECM Battery Feed

Heated Windshield

Engine Ignition Feed

Alternator

IGN/ Fuel Injector Control module

ECM Ignition Feed

Fuel Heater

Maf / Glow Plug Control Module

Fuse/ CB

Amperage

Circuit Protected

40A

Starter Circuit

20A CB

Parking Lights

30A CB

Headlights

30A CB

HVAC

30A CB

Power Windows

30A

CTIS Compressor

40A

ABS/TT4 Hyd. Pump

40A

Ignition Switch Batt Feed

30A

Auxiliary power stud A

30A

Auxiliary power stud B

12-22

Electrical System

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Figure 12-21: Auxiliary Power Studs

Ground Points

Two main grounding points are provided to ground vehicle systems and add-on items. The main grounding stud is located on the
driver’s side of the engine compartment next to the exterior fuse box. The second grounding point is located to the left of the instru-
ment panel on the interior of the vehicle.

NOTE: Never drill holes in the body to ground electrical items, the corrosion resistance is compromised, and bad grounding could
result.

BATTERY CHARGING

General Information

A low charge or discharged battery can be recharged as long as the cells are not shorted, sulfated, or damaged. Batteries can be re-
charged quickly at 20 amp charge levels, or for longer periods at 10, 5, or 2 amps. A 5 amp charge is preferable.

The battery charger should be equipped with a polarity sensor to avoid damage through incorrect hookup. Charger capacity should
range from 5 to 20 amps for slow and fast charge rates.

The time and amp rate of charge required will vary depending on battery condition and temperature. Generally, it takes longer to
recharge a cold battery. State of charge will also affect charging time as a partially discharged battery may only require one third
the charge time of a fully discharged battery. There are a number of safety precautions that must be observed before charging a bat-
tery. The following precautions are necessary to avoid personal injury:

Battery Charging Precautions

• Battery electrolyte contains sulfuric acid which can cause severe burns. Avoid contact with electrolyte by wearing protective

gloves and a face shield. Flush skin or eyes with water if contact occurs and seek medical assistance immediately.

• Always wear eye and facial protection when connecting charging equipment.

• Never attempt to charge a frozen battery. The case could fracture at the first surge of current.

• Never charge a battery with a low electrolyte level. Internal arcing and battery explosion could occur.

• Never exceed a 20 amp charge with a cold battery. Use a lower (5-10 amp) rate until the battery warms up.

• Never use excessive charge rates. Reduce charge rate if the battery becomes overly warm, or if a steady stream of gas starts

to exit the vents.

• Do not use high charge rates on a completely discharged battery. Use low rates or a trickle charge only.

• Never allow sparks, or an open flame near a charging battery. The charging process generates hydrogen gas which is highly

inflammable.

• Charge batteries in properly ventilated areas only. Do not allow hydrogen gas to accumulate and concentrate in poorly ven-

tilated areas.

EXTERNAL FUSE BOX

POWER STUD

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Electrical System 12-23

Charge Rate and Time

Charge rate will depend on battery temperature and degree of discharge. Ideally, charging should not proceed until battery temper-
ature has reached 60°F (16°C). However, in cases where a cold battery must be charged, start with a 5 amp rate and increase it as
battery temperature rises.

In the case of a fully discharged battery, a 24 hour trickle charge of 1-2 amps is recommended. A 20 amp charge rate should be
used when a battery is only partially discharged.

Suggested charge times are outlined in the charge rate chart (Figure 12-22). Note that the chart suggested times and rates are for a
battery at 70°F (21°C). Charge times will be greater if battery temperature is below 55°F (13°C).

Figure 12-22: Charge Rate Chart

Battery Checking Procedures

Visual Inspection

Check for obvious damage, such as a cracked or broken case or cover or overcharging of the electrical system that could permit
loss of electrolyte. If obvious damage is noted, replace the battery.

Load Test

Before proper testing, the battery must be in a fully charged state to obtain an accurate test. Load testing requires the use of battery
side terminal adapters to ensure good connections. Do not attempt to load test a side post battery by screwing bolts into the termi-
nals as connections.

NOTE: When load testing, batteries must be disconnected from each other.

Using a battery load tester, measure voltage across the battery terminals. Normal battery voltage should be 12v or higher.
Recent cranking or load testing will lower the normal voltage. If no cranking or load testing has been performed, and battery
voltage is below 12v, replace the battery.

Connect battery load tester to the battery to be tested. If battery has been recently charged, apply a 300 amp load for 15
seconds to remove the surface charge. Skip this step if the battery has not been charged.

Wait 15 seconds for the battery to recover. Apply the necessary load test for the battery being tested. The load required should
be listed on the battery label, if it is not, use the cold crank amperage divided by 2. (300 cca/2=150 cca)This load should be
applied for 30 seconds

If the voltage does not drop below the minimum value, the battery is good and should be returned to service. The battery
temperature must be estimated by feel and by the temperature the battery has been exposed to for the proceeding few hours. If the
battery has been exposed to temperatures below ambient, use the chart below to adjust the minimum test voltage (Figure 12-23).

Figure 12-23: Load Test Values vs.Temperature

Estimated Temperature

Minimum Voltage

70°F(21°C)

9.6

50°F(10°C)

9.4

30°F(0°C)

9.1

15°F(-10°C)

8.8

0°F(-18°C)

8.5

0°F(Below -18°C)

8.0

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