10Si and 15Si Alternator Repair Manual

For Delco-Remy 10Si and 15Si Series Alternators, Type 116 and 136

alternator repair manual end frame test hole detail
Figure 5 -- End Frame Test Hole


Repair Manual - Troubleshooting Procedures
How to Troubleshoot the 10Si and 15Si, Type 116 and 136 Alternators

Close adherence to the following repair manual in the order presented will lead to the location and correction of charging system defects in the shortest possible time. Only a portion of these procedures need to be performed. It will never be necessary to perform all the procedures in order to locate the trouble.

Either one of two methods may be used to troubleshoot the charging system. One method uses alternator tester Model J-26290. The other method follows:

  • Do not polarize the alternator.
  • Do not short across or ground any of the terminals in the charging circuit, except as specifically instructed herein.
  • Never operate the generator with the output terminal open-circuited.
  • Make sure the alternator and battery have the same ground polarity.
  • When connecting a charger or a booster battery to the vehicle battery, connect negative to negative, and positive to positive.

Note: In some circuits, an ammeter or voltmeter may be used instead of an indicator lamp. In this case, Section "A" pertaining to abnormal indicator lamp operation, should be omitted from the troubleshooting procedure.

Trouble in the charging system will show up as one or more of the following conditions:

  1. Abnormal indicator lamp operation.
  2. Abnormal charging system operation.

A. Abnormal Indicator Lamp Operation

Check the indicator lamp for the normal operation as shown below.

Switch Lamp Engine
Off Off Stopped
On On Stopped
On Off Running

If the indicator lamp operates normally, proceed to "Abnormal Charging System Operation." Otherwise, proceed to either on of the following three abnormal conditions.

  1. Switch Off, Lamp On -- In this case, disconnect the connector from the alternator No. 1 and No. 2 terminals. If the lamp stays on, there is a short between these two leads. If the lamp goes out, replace the bridge rectifier as covered in the "Alternator Repair" section. This condition will cause an undercharged battery.

  2. Switch On, Lamp Off, Engine Stopped -- This condition can be caused by the defects listed in Part 1 above, or by an open in the circuit. To determine where an open exists, proceed as follows:

    1. Check for a blown fuse, a burned out bulb, defective bulb socket, or an open in No. 1 lead circuit between the alternator and ignition switch.
    2. If no defects have been found, proceed to " Abnormal Charging System Operation."
  3. Switch On, Lamp On, Engine Running -- Check for a blown fuse (where used) between indicator lamp and switch. The other possible causes of this condition are covered in the "Abnormal Charging System Operation" section.

If a defect has been found and corrected at this point, no further checks need to be made.

B. Abnormal Charging System Operation

  1. Insure that the undercharged condition has not been caused by accessories having been left on for extended periods.
  2. Check the drive belt for proper tension.
  3. If battery defect is suspected, consult manufacturers instructions for testing.
  4. Inspect the wiring for defects. Check all connections for tightness and cleanliness, including the slip connectors at the alternator and firewall, and connections at the battery.
  5. With ignition switch on and all wiring harness leads connected, connect a voltmeter from:
    1. Alternator " BAT " terminal to ground.
    2. Alternator No. 1 terminal to ground.
    3. Alternator No. 2 terminal to ground.
    A zero reading indicates an open between voltmeter connection and battery. Operate engine at moderate speed. If voltage is 15.5 or more, remove alternator for repair.
  6. With all accessories turned off, connect a voltmeter across the battery. Operate engine at moderate speed. If voltage is 15.5 or more, remove generator for repair.
  7. If previous Steps 1 through 6 check satisfactorily, check alternator as follows:
    1. Disconnect battery ground cable.
    2. Connect an ammeter in the circuit at the " BAT " terminal of the alternator.
    3. Reconnect battery ground cable.
    4. Turn on accessories. Connect a carbon pile across the battery.
    5. Operate engine at moderate speed as required, and adjust carbon pile as required to obtain maximum current output.
    6. If ampere output is within 10 amperes of rated output as stamped on alternator frame, alternator is most likely not defective; recheck Steps 1 through 6. Important: If output in amperes is OK, but indicator lamp stays on, check diode trio and rectifier bridge in "Generator Repair" section.
    7. If ampere output is not within 10 amperes of rated output, determine if test hole ( Fig. 5) is accessible. If accessible go to Step h. If not accessible go to step l.
    8. Ground the field winding by inserting a screwdriver into the test hole (Fig. 5). Caution: Tab is within 3/4 inch of casting surface. Do not force screwdriver deeper than one inch into end frame.
    9. Operate engine at moderate speed as required, and adjust carbon pile as required to obtain maximum current output.
    10. If output is within 10 amperes of rated output, check field winding as covered in "Generator Repair" section, and test regulator with an approved regulator tester.
    11. If output is not within 10 amperes of rated output, check the field winding, diode trio, rectifier bridge, and stator as covered in "Alternator Repair" section.
    12. If test hole is not accessible, disassemble alternator and make tests listed in "Alternator Repair" section.