Symptoms
- Battery-shaped icon lights up on the dash
- Dimming headlights or interior lights
- Radio or electronics acting oddly
- Car may struggle to start or stall while driving
Likely causes
- CommonFailing alternatorThe alternator recharges the battery while driving; when it fails, the battery slowly drains.
- CommonLoose or worn serpentine beltIf the belt slips or breaks, the alternator can't spin to charge.
- CommonCorroded or loose battery terminalsPoor connections interrupt charging even with a good alternator.
- PossibleFailing batteryAn old battery can't hold a charge even when charging is working.
- Less commonWiring or charging system fuse issueLess common but possible on any vehicle.
What to do
- Turn off nonessential electronics like the radio and AC to reduce electrical load.
- Check if the serpentine belt is visibly loose, cracked, or missing.
- Look at the battery terminals for corrosion (white or greenish buildup) and make sure cables are tight.
- Avoid long drives; if the alternator has failed, the battery will run down and the car will eventually stall.
- Get to a parts store or mechanic while the car still runs to have the battery and alternator tested.
- Ask for a load test on the battery and a charging output test on the alternator.
- Replace whichever component tests bad rather than guessing.
- Clean corroded terminals with a wire brush and a baking soda and water mix if that's the issue.
Tools and parts
- Wrench set
- Wire brush (for terminal corrosion)
AlternatorSearch: “alternator for your car make, model, year”
Serpentine beltSearch: “serpentine belt for your car make, model, year”
Car batterySearch: “group size car battery for your model”
When to call a pro
See a mechanic promptly to test the alternator and battery before you're stranded with a dead battery.
Safety
Use caution
The engine can stall unexpectedly while driving if the battery runs out of charge; avoid highway driving once this light appears.