System Diagnosis - Charging System - Bosch

1. Visually check belt and wiring and make necessary repairs.
2. With ignition switch in RUN position and engine stopped, the charge indicator lamp should be on. If it is not on, disconnect harness at generator and ground negative terminal in harness with a fused jumper lead. If lamp lights, replace generator. If lamp does not light, locate open in circuit between ignition switch and harness connector and check for burned out indicator lamp.
3. With ignition switch in RUN position and engine running at a moderate speed, the charge indicator lamp should be off. If it is not off, disconnect harness at generator. If lamp goes off, replace generator. If lamp stays on, check for a short to ground in harness between connector and indicator lamp.
4. Check battery for an overcharged or undercharged condition as follows:
a. Attach a suitable voltmeter, ammeter and carbon pile to vehicle.
b. With ignition switch in OFF position, check and record battery voltage.
c. Remove harness connector from generator.
d. Turn ignition switch to Run position and check voltage at the brown wire in harness. Battery voltage should be present. If battery voltage is not present, check charge indicator circuits for open or grounded circuits causing voltage loss and repair as necessary.
e. Reconnect generator harness connector.
f. Run engine at a moderate idle and measure voltage across battery terminals. Voltage should read more than recorded in step B and less than 16 volts. If reading is not as specified, replace generator.
g. Run engine at a moderate idle and check generator amperage output. Adjust carbon pile load to obtain maximum amperage while maintaining battery voltage above 13 volts. If amperage reading is within 15 amps of generators rating, generator is functioning properly. If amperage is not within 15 amps, replace generator.
h. With generator operating at maximum output, measure voltage between generator housing and battery negative terminal. Voltage drop should be .5 volt or less. If more than .5 volt, check ground path from generator housing to battery negative and determine cause of voltage drop. Repair loose or corroded ground connections as necessary.