* Alternator Failure: The alternator charges the battery. If it fails, the battery quickly drains, leaving no power for the electrical system and the engine to start. This is a very common cause.
* Battery Failure (Less likely in this scenario): While a dead battery can cause a no-start, the suddenness suggests more of a charging problem (alternator) than a complete battery failure. However, a severely degraded battery *could* also exhibit this behavior.
* Loose or Corroded Battery Cables: Poor connections can prevent the battery from supplying power, even if the battery and alternator are fine.
* Fuses or Relays: A blown fuse or failed relay could interrupt power to crucial parts of the electrical system. This is less likely to cause a *complete* electrical shutdown, but it's worth investigating.
* Wiring Problem: A short circuit or damaged wiring harness could interrupt power flow. This is less likely but possible.
* Ignition Switch: While less common, a failing ignition switch could cut power to the entire system.
What to do:
1. Check the battery cables: Inspect them for corrosion and ensure they're securely connected to both the battery and the starter motor. Clean any corrosion with a wire brush and baking soda.
2. Jump start the car (with caution): If you have jumper cables and another vehicle, try jump-starting the car. If it starts and runs, the problem is likely the alternator or the battery. If it doesn't start, it points to a more serious electrical problem.
3. Have the alternator and battery tested: A mechanic or auto parts store can test both to determine their condition. This is the most crucial step.
4. Check fuses and relays: Consult your owner's manual to locate and inspect fuses and relays.
5. If the above steps don't solve the issue: You will need a mechanic to diagnose the problem further. They may need to use diagnostic tools to pinpoint the electrical fault.
Important Safety Note: If you suspect a problem with the electrical system, avoid working on it yourself unless you are experienced and comfortable with automotive electrical systems. Improper handling can lead to shocks or other injuries.
