TM 10-3930-671-24 6.8. Alternator Maintenance Troubleshooting Guide ................................................................... F-261 Alternator Maintenance Precautions .............................................. F-262 Alternator Inspection ...................................................................... F-262 Troubleshooting Procedures .......................................................... F-262 Alternator Installation...................................................................... F-264 Altemator Mounting Parts - GPX Model - TMD 27 [2.7L] Engine... F-265 Troubleshooting Guide Problem Probable Cause Corrective Action 1 Battery undercharged 1 Defective cables, dirty posts, 1 Check, clean, repair or replace a) ammeter (if used) indicates corroded terminals, etc.  as needed. constant discharge 2. Loose or broken belt 2. Check belt. b) indicator lamp remains on 3. Worn or broken brushes 3. Replace brush assembly. 4. Defective alternator system 4. Repair or replace alternator. 2. Battery undercharged 1. Indicator lamp burned out or 1. Check bulb & harness. a) indicator lamp OFF with key defective wiring harness. ON and engine stopped. 2. Plug at rear of altemator. 2. Check plug to ensure it is (Normal condition is lamp ON) fully seated. 3. Broken brush 3. Replace brush assembly. 4. Defective alternator system 4. Replace regulator. 3. Battery overcharges 1. Plug at rear of alternator or 1. Repair or replace components. a) excessive use of water wiring harness. b) ammeter (if used) shows 2. Defective alternator system. 2. Repair or replace regulator. constant excessive charge. c) voltmeter indicates greater than 14.5 volts (connected across battery with no load) with engine idling. 4. Battery charges at idle, 1. Slipping belts. 1. Check belts and adjust tension but discharges under load or replace, as necessary. conditions 2. Altemator defective 2. Repair or replace alternator. 5. Indicator lamp glows slightly 1. Defective diode trio 1. Replace diode trio. under moderate load; battery appears charged. Also refer to: Section 6.9, Prestolite Altemator Service Manual. F-261

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