GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1996 🢒 DeVille 🢒 Engine 🢒 Engine Electrical 🢒 Battery Is Undercharged or Overcharged

Step

Action

Value(s)

Yes

No

1*

Perform the charging system message and code diagnosis.

Is there a message or a code?

--

System OK.

Go to Step 2

2
  1. Check the connections at battery, G101, generator.
  2. Battery fully charged.
  3. Turn off all electrical leads.
  4. Connect the voltmeter to the generator output.
  5. Run the engine at 2500 RPM for 30 seconds.
  6. Check the voltage output.

Is the voltage 16 volts or greater?

--

Go to Step 3

Go to Step 4

3**

Perform generator disassembly, test and reassembly (Section 6D3).

Does the rotor pass the ohmeter check?

--

Replace the regulator.

Replace the rotor and regulator.

4
  1. Connect an inductive ammeter to the battery charging cable from the generator.
  2. Connect a carbon pile across the battery.
  3. Run the engine at 2500 RPM and adjust the carbon pile to obtain maximum output from the generator. Note the value.
  4. Run the engine at idle and adjust the carbon pile to obtain maximum output. Note the value. Verify the correct idle speed.

Is the generator OK? (Generator output shold be greater than 90% of rated output at 2500 RPM and 45 amps at idle.)

--

Got to Step 6

Go to Step 5

5***

Perform generator disassembly, test, and reassembly. Refer to Section Charging.

Were the procedures performed?

--

System OK

--

6

With the engine running, measure the voltage drop between the generator housing and the battery negative terminal.

Is the voltage greater than 0.2 volts?

--

Check for poor ground/high resistance in the ground path.

Fault not present.

7
    • *Always diagnose codes before performing the functional check. This will test the PCM's ability to detect generator faults and out of range voltage conditions.
    • **Over-voltage conditions may be caused by: defective rotor or regulator. Overcharging may be evidenced by low electrolyte level in the battery.
    • ***Insufficient amperage output may not set codes but result in marginal battery charging if driving habits involve short trips and prolonged idling, especially in warmer weather. Low output may be caused by: a defective refulator, an open or shorted diode, contamination of brushes. No output conditions may be caused by: a defective refulator, an open or shorted rotor, stator damage, brushwear.
    • When all diagnosis and repairs are completed, clear codes and verify operation.