GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1998 🢒 GMC Suburban - 4WD 🢒 Engine 🢒 Engine Electrical 🢒 Battery Operation

Battery Operation Undercharged or Overcharged

Step

Action

Value(s)

Yes

No

1
  1. Disconnect the generator connector.
  2. Place the ignition switch in the RUN position.
  3. Connect a voltmeter from BRN (25) wire at the generator connector to ground.

Does voltmeter read battery voltage?

12 V

Go to Step 2

Go to Step 4

2

Connect the voltmeter from terminal BAT at generator to ground.

Does voltmeter read battery voltage?

12 V

Go to Step 3

Go to Step 6

3
  1. Connect the generator connector.
  2. Have all accessories turned off and the engine running at fast idle.
  3. Connect the voltmeter across battery terminals and note the voltage.

Is the voltmeter reading within range?

13-16 V

Go to Step 7

Go to Step 8

4

Backprobe BRN (25) wire at the instrument cluster connector with a voltmeter to ground

Does voltmeter read battery voltage?

12 V

Go to Step 9

Go to Step 5

5

Backprobe PNK (39) wire at the instrument cluster connector terminal 22 with a voltmeter to ground.

Does battery voltage exist?

--

Go to Step 10

Go to Step 11

6

Repair or replace the black/red wire from the fusible link to generator.

Is the repair complete?

 

System OK

--

7

Perform battery load test. Refer to Battery Load Test .

Is the test complete?

--

System OK

--

8

Perform generator bench test. Refer to Generator Assembly Bench Check .

Is the generator okay?

--

Go to Step 7

9

Locate and repair open in BRN (25) wire from the instrument cluster to generator.

Is the repair complete?

--

System OK

--

10

Check the charge indicator filament.

Is the charge indicator filament okay?

--

Go to Step 12

--

11

Locate and repair open in PNK (39) wire from the I/P fuse block to the instrument cluster.

Is the repair complete?

--

System OK

--

12

Replace the instrument cluster.

Is the replacement complete?

--

System OK

--

Battery Operation Causes of Battery Failure

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:

  1. A vehicle accessory was left on overnight.
  2. The driving speeds have been slow with frequent stops ("stop-and-go" driving).
  3. The electrical load has exceeded the generator output (particularly with the addition of aftermarket equipment).
  4. Existing conditions in the charging system, including the following possibilities (refer to Section 8A):
    5. • An electrical short
    • A slipping belt
    • A bad generator
    • A bad generator voltage regulator
  5. The battery has not been properly maintained, including the following situations:
    6. • A failure to keep the terminals tight
    • A failure to keep the terminals clean
    • A loose battery hold down
  6. There are mechanical conditions in the electrical system, such as a short or a pinched wire, attributing to power failure. (Refer to Section 8A).