You know those little red warning lights on your car’s console that flash on every once-in-a-while? They say things like “check engine”, “check oil”, “tire pressure”, or “ALT”. Those little lights aren’t coming on just for your viewing pleasure—they’re coming on to let you know some kind of maintenance is needed on your vehicle. And, if you’ve avoided that 30,000-mile check or ignored that oil change every three months it’s likely pretty important that you get the lights checked out by an automotive professional.
If your “ALT” light comes on for example, it may mean that the alternator output voltage is lower than the battery voltage. It could also imply that the battery voltage is lower than the alternator output voltage. And, if the “ALT” light dims as you rev up the car’s engine, then your alternator might need work. If the light grows brighter, then the car’s battery could be bad.
