J 39200 Digital Multimeter
1. Check the belt for wear and tension. Refer to SECTION 6B1 for belt diagnosis. Check the wiring.
2. With the ignition switch on and the engine off, the lamp should be on. If not, detach the wiring harness at the generator and use a fused jumper wire (J 36169 or equivalent with a 5-amp fuse) to ground the “L” terminal lead in the wiring harness (figures).
• If the lamp lights, replace the generator.
• If the lamp does not light, locate the open circuit between the grounding lead and the ignition switch. The lamp may be open.
3. With the ignition switch on and the engine running at moderate speed, the lamp should be off. If not, stop the engine, turn the ignition switch on, and disconnect the wiring harness at the generator.
• if the lamp goes out, replace the generator.
• If the lamp stays on, check for a grounded “L” terminal wire in the harness.
4. If the battery is undercharged or overcharged or the vehicles voltmeter shows high or low voltage with the engine running:
A. Disconnect the wiring harness connector from the generator.
B. With the ignition switch on and the engine not running, connect J 39200, set on DC voltage scale, from ground to the “L” terminal in the wiring harness. Voltage should be B+, other readings indicate an open, high resistence or grounded circuit between the terminal and the battery. Correct as required.
C. Connect the harness connector to the generator and run the engine at 2500 RPM with accessories off.
D. Measure the voltage across the battery. If it is above 16 volts, replace the generator.
E. With the engine off, connect an ammeter at the generator output terminal. The ammeter must have the capability to measure 115 amps of current. Connect J 39200 across the generator and a carbon pile across the battery.
• Run the engine at 2500 RPM, turn on the accessories, and load the battery with a carbon pile to obtain maximum amperage.
Maintain voltage at 13 volts or above.
• If the output in amperes is within 15 amperes of the rated output, the generator is OK. Refer to “Specifications.”
• If the output is not within 15 amperes of the rated output, replace the generator.