Battery / charging system light
A battery shape with + and - terminals, usually red
Do not keep driving it · Red means stop
Battery / charging system light
Stop driving as soon as you safely can and get the car looked at. This light does not mean the battery is flat right now — it means the car has stopped charging while the engine is running, and everything electrical is living off whatever charge is left in the battery. Once that runs out, the engine will stall and won't restart, and you'll lose power steering and power brake assist right before it does. That can happen in a few minutes or over an hour, depending on the car and how much you're asking of the electrical system. There's no safe way to know which, so treat it as short notice.
This light means the car's charging system — the alternator, the belt that drives it, or the wiring and connections around it — is not putting power back into the battery. It's a different problem from a battery that's simply old or drained. A car with a dead battery usually won't start at all. A car with this light on has started fine and is running, but the charging system has dropped out somewhere along the way.
The most common cause is a worn or broken drive belt, or a belt tensioner that's failed, so the alternator isn't spinning. Next most common is the alternator itself wearing out — brushes, diodes, or the internal regulator failing with age. After that, it can be a bad connection or corroded terminal at the battery or alternator, or wiring damage. Less often, it's the battery itself failing in a way that confuses the charging system, or on some newer cars, a fault in the wiring or module that manages charging.
Sorting it out starts with a check of the belt and a test of the charging voltage at the battery with the engine running. That usually shows pretty quickly whether the alternator is putting out power or not. If the belt is the problem, that's a straightforward replacement. If it's the alternator, it typically needs to come out and be replaced or rebuilt, and battery condition gets checked at the same time since a struggling alternator can shorten a battery's life. Wiring and connection problems take more time to track down since they can be anywhere in the circuit. We can tell you more once we've had a look, but don't plan on driving it any real distance until it's checked.