Quick Answer: If your lights, radio, or dash come on but the engine won’t crank, the battery is not completely dead, it has enough juice for accessories but not enough to power the starter motor. This is classic low battery voltage. You need a jump start or a new battery. It could also be a bad starter or a faulty connection. Start with a jump and go from there.
What To Do
- Try a jump start first. This confirms whether the battery is the issue. If the car starts after a jump, the battery is weak or failing.
- Drive to an auto parts store immediately. Most stores (AutoZone, O’Reilly, Advance Auto) test your battery and alternator for free. Do not turn the car off until you arrive.
- If it won’t start after a jump, the problem is likely the starter motor, not the battery. The jump confirmed the battery has some charge, the starter isn’t engaging.
- Check battery terminals. Look for loose connections or heavy corrosion (white/blue-green buildup). A corroded terminal causes exactly this symptom, lights work, car won’t start.
- If terminals are corroded, clean them with a wire brush or terminal cleaner spray, reconnect firmly, and try again.
- If the car clicks when you turn the key, read the clicking article, one click is usually the starter solenoid, rapid clicks are low battery.
Why Lights Work But the Car Won’t Start
The starter motor draws 80–200 amps when cranking. Your headlights draw about 10 amps. A battery sitting at 11.5 volts can power lights all day but can’t deliver the surge current the starter needs. This is the most common reason for this symptom.
| Likely Cause | Test |
|---|---|
| Weak/failing battery | Jump start the car |
| Corroded terminals | Visual inspection, wiggle test |
| Bad starter motor | Jump doesn’t help, hear one click |
| Faulty ground cable | Lights flicker, inconsistent behavior |
| Bad alternator (battery won’t hold charge) | Battery keeps dying after charges |
What It Might Cost
| Fix | Typical Cost |
|---|---|
| Battery replacement | $100 – $220 installed |
| Terminal cleaning | $20 – $50 at a shop |
| Starter replacement | $300 – $600 |
| Ground cable replacement | $50 – $150 |
| Alternator replacement | $400 – $800 |
Before spending money, get the battery tested. A battery that’s 5+ years old and showing this symptom is overdue for replacement regardless of the test result.
Stay Safe
- When jumping the car, make sure both vehicles are off before connecting cables. Connect positive to positive, then negative to a metal ground on the dead car, not to the battery negative post. This prevents sparking near the battery.
- Don’t jump a cracked or leaking battery. If you see bulging, cracks, or fluid on the battery, do not jump it. Call a tow.
- If the battery dies again within a few days after jumping or replacing it, the alternator is probably not charging it properly. Get the charging system tested.
- In cold weather, battery capacity drops significantly. A battery at 20°F might start fine in summer but fail completely in winter. Cold-weather failures are common in older batteries.