GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

DEFINITION: Generator on-vehicle test which will test the generator independently from the vehicle wiring.

1

Did you perform the Charging System Check ?

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Go to Step 2

Go to Charging System Check

2

  1. Connect the red alligator clip of a J 41450-B CS Generator Electronic Tester to the generator output terminal. (The output wire is attached to the generator with a ring terminal and nut.)
  2. Connect the black alligator clip of the J 41450-B to the metal generator housing. The green POWER lamp of the tester should light and remain lighted while the tester is being used.

Does the green POWER lamp on the tester light?

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Go to Step 9

Go to Step 3

3

  1. Recheck the alligator clip connections that were made in Step 2.
  2. Correct the connections if they were reversed.

Does the green POWER lamp on the tester light after the correct connections are verified?

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Go to Step 9

Go to Step 4

4

Connect a J 39200 digital multimeter (DMM) from the generator output terminal to the generator metal housing.

Is the measured voltage within the specified range?

Above 12 V

Go to Step 18

Go to Step 5

5

Use a DMM to check the voltage between the battery terminals.

Is the measured voltage within the specified range?

Above 12 V

Go to Step 6

Go to Step 8

6

  1. Inspect the circuit between the generator output terminal and the battery positive terminal for a loose connection or open circuit condition. Be sure to check for an open fusible link and/or any blown in-line fuses that may be used on the vehicle.
  2. If a loose connection or open circuit was located, repair it. If an open fusible link or blown fuse was found, be sure to check the system for possible causes of a circuit overload, such as a direct B+ short to ground.

Is the circuit okay between the generator output terminal and the battery positive terminal?

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Go to Step 7

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7

Repair the loose connection or open circuit between the battery negative terminal and the generator housing.

Is the repair complete?

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Go to Step 26

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8

  1. Inspect the battery. Refer to Battery Load Test .
  2. Charge or replace the battery if necessary.

Is the battery OK?

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Go to Step 26

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9

  1. Leave the J 41450-B alligator clips attached as in Step 2, and disconnect the vehicle 4-way generator connector.
  2. Locate the matching 4-way connector of the J 41450-B and connect it to the generator.

Does the red DIAGNOSTIC lamp on the tester light?

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Go to Step 11

Go to Step 10

10

Perform the following test of the DIAGNOSTIC lamp of the J 41450-B :

  1. Disconnect the J 41450-B 4-way connector from the generator, but leave the J41450-B alligator clips connected as in step 2.
  2. Prepare a jumper wire with an in-line 100 ohm resistor. The watt rating of the resistor is not important. (An inexpensive 100ohms resistor can be purchased at an electronics supply store.)
  3. At one end of the prepared jumper wire, attach a Metri-Pack 150 male terminal probe adapter from a J 35616 Connector Test Adapter Kit.
  4. Connect the prepared jumper wire to the J 41450-B L terminal (which is called the B terminal on CS 130D, LR, and AD generators). The tester connector terminals are the same as the generator connector terminals, so terminal identification on the J 41450-B can be accomplished by referring to Starting and Charging Connector End Views.
  5. Connect the other end of the jumper to the battery negative terminal.

Does the red DIAGNOSTIC lamp on the tester light when the jumper is connected?

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Go to Step 19

Go to Step 18

11

Caution: Make sure that the load is completely turned off before connecting or disconnecting a carbon pile load tester to the battery. Otherwise, sparking could ignite battery gasses which are extremely flammable and may explode violently.

  1. Prior to connecting a carbon pile load tester, make sure that the load dial of the carbon pile tester is turned completely to the OFF position.
  2. Connect the cable leads of the carbon pile tester to the battery of the vehicle.
  3. Connect an inductive ammeter to the output lead(s) of the generator. Make sure that all output leads pass through the ammeter inductive clip. The carbon pile tester may have its own inductive ammeter, or use a J 35590 Current Clamp.
  4. Start the engine and allow it to idle briefly.

Does the red DIAGNOSTIC lamp on the J 41450-B light?

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Go to Step 19

Go to Step 12

12

Increase the engine speed to 2500 RPM.

Does the red DIAGNOSTIC lamp on the J 41450-B light?

--

Go to Step 19

Go to Step 13

13

  1. Maintain the engine speed at 2500 RPM.
  2. Turn on the load of the carbon pile tester, and increase the load until the generator output is equal to the load test value given in Generator Usage.

As the load is increased, is the generator capable of producing the amount of load test current specified in Generator Usage ?

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Go to Step 14

Go to Step 19

14

Maintain the engine speed at 2500 RPM and continue to operate the generator at the load test value.

Is the red DIAGNOSTIC lamp on the J 41450-B lit?

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Go to Step 19

Go to Step 15

15

  1. Maintain the engine speed at 2500 RPM and continue to operate the generator at the load test value.
  2. Connect a DMM from the generator output terminal to the battery positive (+) terminal.

Is the measured voltage within the specified range?

Above 0.5 V

Go to Step 22

Go to Step 16

16

  1. Maintain the engine speed at 2500 RPM and continue to operate the generator at the load test value.
  2. Connect a DMM from the generator metal housing to the battery negative (-) terminal.

Is the measured voltage within the specified range?

Above 0.5 V

Go to Step 23

Go to Step 17

17

Caution: Make sure that the load is completely turned off before connecting or disconnecting a carbon pile load tester to the battery. Otherwise, sparking could ignite battery gasses which are extremely flammable and may explode violently.

  1. Disconnect the DMM.
  2. Turn OFF the load in the carbon pile tester.
  3. Turn the ignition switch to LOCK to stop the engine.
  4. Disconnect the carbon pile tester cables from the battery.
  5. Disconnect the J 41450-B 4-way connector from the generator.
  6. Inspect the generator 4-way connector on the vehicle.

Does the vehicle have a wire in the L terminal cavity (or B terminal for CS 130D, LR, and AD generators) of the generator 4-way connector?

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Go to Step 26

Go to Step 24

18

There is an internal problem in the J 41450-B . Replace the J 41450-B .

Has the J 41450-B been replaced?

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Go to Step 26

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19

Important: Before generator repair or replacement, the L terminal circuit (if applicable) must be tested for resistance in order to avoid a repeat failure.

Disconnect and examine the generator 4-way connector.

Is there a wire in the L cavity (or B cavity for CS 130D, LR, and AD generators) of the generator connector?

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Go to Step 20

Go to Step 24

20

  1. Be sure the 4-way generator connector is disconnected.
  2. Turn the ignition key to the RUN position.
  3. Connect a fused jumper wire J 36169-A (with a 5 amp fuse) from ground to the vehicle 4-way generator connector terminal L (or B terminal for CS 130D, LR, and AD generators). To connect the jumper to the generator, use a Metri-Pack 150 connector test adapter from J 35616 . Refer to Starting and Charging Connector End Views.

Does the fuse blow?

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Go to Step 21

Go to Step 25

21

There is a short to B+ voltage when the ignition key is in the RUN position. The short may be a result of a miswired condition. The L terminal circuit must be a resistance circuit either through a charge indicator or the PCM. If direct battery voltage is applied to the generator at the L terminal, the regulator will eventually be destroyed, causing a repeat failure. Repair the short to B+ voltage in the L terminal circuit (or B terminal circuit for CS 130D, LR, and AD generators).

Is the short circuit repaired?

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Go to Step 25

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22

  1. Turn off the engine.
  2. Disconnect the battery negative terminal.
  3. Inspect the circuit between the battery positive terminal and the generator output terminal for a high-resistance connection. Disassemble and clean all connections in this circuit.
  4. Assemble the connections and tighten to specifications.
  5. Connect the battery negative terminal. Tighten to specifications. Refer to Fastener Tightening Specifications.

Is the repair complete?

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Go to Step 26

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23

  1. Turn off the engine.
  2. Inspect the ground circuit for high resistance from the battery negative terminal to the generator housing. Disassemble and clean all connections.
  3. Assemble the connections and tighten to specifications. Refer to Fastener Tightening Specifications.

Is the repair complete?

--

Go to Step 26

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24

The tester turns the generator on in a different way than the vehicle does, so an additional test is necessary. This Step is applicable only for vehicles that do not use an L terminal connection (or B terminal for CS 130D, LR, and AD generators).

  1. Remove the 4-way connector from the generator.
  2. Measure the generator internal resistance between the L and I/F terminals (B and C terminals for CS 130D, LR, and AD generators). Use Metri-Pack 150 terminal adapters from a J 35616 Connector Test Adapter Kit. The L and I/F terminals are the two middle terminals on the generator.

Is the measured resistance within the specified range?

Below 500 ohms

Go to Step 26

Go to Step 25

25

Repair or replace the generator. Refer to Generator Replacement.

Is the repair complete?

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Go to Step 26

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26

  1. Make sure any components removed during diagnosis are installed in place and that all connectors are connected.
  2. Repeat the system check. Refer to Charging System Check .

Is the system check complete?

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System OK

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