Tools Required OLD

J 39200 Digital Multimeter

An undercharged battery is usually characterized by slow cranking or by a dark battery hydrometer. If this condition exists, check the following items for a cause.

1. Determine that the undercharged condition has not been caused by leaving accessories on for extended periods without charging the battery.
2. Check the drive belt for proper tension. Refer to Generator Replacement in this section.
3. If battery fault is suspected, refer to Battery Common Causes of Malfunction in this section.
4. Inspect the wiring for faults. Check that all connections are clean and tight. Also check that all bulkhead connectors are tight and undamaged. Battery cable connections at the battery, starter and engine ground points should also be checked.



5. With all accessories turned off, connect a J 39200 across the battery. Run the engine at a moderate speed and check the voltage, taking into account the temperature the generator is exposed to during the test. As the temperature of the regulator case (2) in the generator increases, the voltage output will decrease. The standard regulator voltage setting (1) is 14.2 to 14.8 volts at 25°C (3) (77°F (4)). The minimum operating voltage should be 13.5 volts. If the voltage is at 13.5 volts or more, proceed to the next step. If the voltage is less than 13.5 volts, remove the generator. Refer to Generator Replacement .
6. If the previous steps have not produced satisfactory results, perform the following generator test.

6.1.	Disconnect the negative (-) battery cable.

6.2.	Remove the rubber protector, the nut and the generator battery terminal wire.





6.3.	Connect an ammeter (1) between the generator (2) and the disconnected wire. Connect the ammeter black lead to the wire and the ammeter red lead to the generator battery terminal.

Connect a J 39200 between the generator battery terminal and the chassis ground.

6.4.	Start and run the engine at 2,000 RPM. Turn all accessories and high-beam headlamps on. Turn the blower to HIGH. Ground the generator F terminal with a screwdriver.

6.5.	Adjust the engine speed to obtain the maximum current output.

6.6.

If the current output is within 10 amperes of the maximum rating and the voltage reading is 13.5 to 16.0 volts, the generator is not faulty and is not the cause of an undercharged battery condition. If the current output is not within 10 amperes of the maximum rating, or the voltage reading is less than 13.5 volts, remove the generator. Refer to Generator Replacement or Generator Overhaul .

If an obvious overcharge condition exists (as evidenced by spewing of electrolyte), test the field windings for shorts and grounds. If the field winding is faulty, replace the rotor and retest the generator for proper voltage output. Refer to Generator Replacement or Generator Overhaul .

1. Connect a fast charger and a J 39200 to the battery.
2. Turn the ignition switch to ON and slowly increase the charge rate. The indicator in the vehicle will begin to dim when the voltage setting is reached. The indicator should dim at 13.5 to 16.0 volts. If the test results are unsatisfactory, replace the voltage regulator. Refer to Generator Replacement or Generator Overhaul .

1. Remove the generator from the vehicle. Refer to
2. Remove the voltage regulator from the generator. Refer to
3. Connect a J 39200 and a fast charger to a fully charged 12 volt battery.
4. Connect the voltage regulator battery terminal to the battery positive terminal.
5. Connect a test lamp across the voltage regulator rotor terminals. If the test lamp lights, proceed to the next step. If the test lamp does not light, replace the voltage regulator.
6. Turn the fast charger on. Observe the J 39200 . The test lamp will begin to dim as the voltage regulator setting is reached. The test lamp should go out at 13.5 to 16.0 volts. If the test results are satisfactory, the voltage regulator is serviceable and should be reinstalled on the vehicle. If the test results are unsatisfactory, replace the voltage regulator.

The test lamp is connected into the circuit exactly as the rotor would be when the regulator is inside the generator. The regulator interrupts the current to the test lamp when the regulator voltage setting is reached. This voltage will vary slightly with temperature variations.