What usually causes it
- A failing alternator, the part that charges the battery while the engine runs
- A broken or slipping serpentine belt, which drives the alternator
- A loose or corroded battery cable or ground connection
- Less often, the battery itself or a wiring fault
What to do
Turn off what you don't need, like the heated seats, rear defrost and radio, and head somewhere safe or to a shop. The car can run on the battery alone for a limited time, and when the battery runs flat it will stall.
If the temperature gauge is climbing too, stop: a broken serpentine belt can also stop the water pump on many engines.
What we do
We test the battery, the alternator output and the belt, and check the connections, so you only replace what's failed. A battery test is $30 & up, and serpentine belt replacement is $100 & up.