Charging System Troubleshooting
By: Parts for Trucks
The following conditions and their possible causes allow for quick reference to charging system troubleshooting tips. However, note that this is only a guide. Before replacing any part or declaring a problem is solved, verify the cause and cure with the proper test equipment.
To use the guide, look at the bolt type to find the problem you are facing. It is followed by one of the possible causes.
THE TRUCK WON’T START
A dead battery: loose or corroded battery connections: ignition circuit or switch malfunction.
ALTERNATOR LIGHT STAYS ON WITH THE ENGINE RUNNING
Loose or worn alternator drive belt: loose alternator wiring connections: short in alternator light wiring: defective alternator stator or diodes: defective regulator.
THE ALTERNATOR LIGHT STAYS OFF WITH THE IGNITION SWITCH ON
Blown fuse; defective alternator; defective indicator light bulb or socket.
ALTERNATOR LIGHT STAYS ON WITH IGNITION SWITCH OFF
Short in alternator wiring: defective rectifier bridge.
LIGHTS OR FUSES BURN OUT FREQUENTLY
Defective alternator wiring: defective regulator; defective battery.
AMMETER GAUGE SHOWS DISCHARGE
Loose or worn drive belt; defective wiring; defective alternator or regulator, defective ammeter or improper wiring connections.
Loose drive pulley; loose mounting bolts; worn or dirty bearings, defective diodes or stator.
THE BATTERY DOES NOT STAY CHARGED
Loose or worn drive belt: loose or corroded battery connections, loose alternator connections: defective alternator or battery: defective alternator stator or diodes; add-on electrical accessories exceeding alternator capacity.
BATTERY OVERCHARGES AND/OR USES TO MUCH WATER
Defective battery: defective alternator, excessive alternator voltage.