Tools Required

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 .
3. If a battery fault is suspected, refer to Battery Load Test .
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 that the generator is exposed to during the test. As the temperature (2) of the regulator case in the generator increases, the voltage output (1) will decrease. The standard regulator voltage setting is 14.2 -14.8 volts at 25°C (3) (77°F). 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, replace the voltage regulator. Refer to Generator Overhaul .
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.

6.4.	Connect a J 39200 (3) between the generator battery terminal and chassis ground.





6.5.	Start and run the engine at 2000 RPM. Turn all accessories and high-beam headlamps on. Turn the blower to HIGH. Ground the generator F terminal with a screwdriver (1).

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

6.7.

If the current output is within 10 amperes of the maximum rating and the voltage reading is 13.5 to 15.1 volts, the generator is not faulty and is not the cause of an undercharged battery condition. Refer to General Specifications . If the current output is not within 10 amperes of the maximum rating, or the voltage reading is less than 13.5 volts, repair or replace the generator. Refer to Generator Overhaul .

If an obvious overcharge condition exists, (as evidenced by the 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 and 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 and Generator Overhaul .