Alternator Output Test
CAUTION:
DO NOT ground "B+" terminal.
- Start engine and verify charge indicator light goes out. If indicator does not go out, go to step 2). If indicator does go out, turn engine off, go to step 5).
- Turn ignition switch to ON position and with engine off. Check voltage readings at each terminal. See ALTERNATOR TERMINAL VOLTAGE table. See Fig 1.
- With engine running at normal curb idle recheck alternator terminal voltages. See ALTERNATOR TERMINAL VOLTAGE table. See Fig 1.Alternator Terminal Voltage
Alternator Terminal Ign. ON/Eng. OFF Volts Engine At Idle Volts B+ Approximately 12 14.1-14.7 "L" Approximately 1 14.1-14.7 "S" Approximately 12 14.1-14.7 - Check wiring harness between battery and B+ terminal if voltage check is okay. Check wiring harness if voltages are below specification. If wiring harness is good, service or replace alternator. See Fig 1.
- Using Rotunda Starting and Charging Tester (078-00005 VAT40), connect positive lead to alternator B+ terminal connector. Connect negative lead to B+ terminal wiring connector and set tester to ammeter function. See Fig 2. Connect Rotunda Inductive Dwell-Tach-Volts Ohms Tester (059-000 10).
- With engine running and all accessories and lights on, depress brake pedal. With engine speed of 2500-3000 RPM, alternator output should be 70 amps or more. If not, recheck belt tension. If belt tension is okay, service or replace alternator.