There should be 12 volts or close to it at the alternator b+ terminal. Possibly a wiring problem,fried fusible link wire or a blown fuse depending on vehicle make and model. Check for blown fuses or check at the starter solenoid for fried fusible link wiring. Some makes ,the PCM computer regulates the voltage...possible PCM problem,again depending on vehicle make..... You didnt specify what kind of vehicle this is...Year,make,model,engine size.... Doc J
Alternator is defective and needs replacing.
You might have a bad battery, a poor connection between the battery and alternator, or a bad ground from the battery.
alternator or bad wires
The alternator may not be recharging the battery .
Defective alternator.
Only if something is wrong. Drive it to your local auto parts store and have them check the system. Most do it for free.
Likely the battery or alternator, but probably the alternator
There is not an alternator indicator light on a Honda Pilot. If the alternator goes out, the battery will not stay charged.
Maybe your alternator needs replacing.
The battery light stays on when the alternator is over or under charging.
Alternator bad or wiring fault to alternator.
Alternator defective, or alternator belt broken or slipping.