when the car battery is bad
If the battery light is on, there is likely a problem. You can also check the voltage meter that should be located near the temperature dial. When your car is on, the volt reading should be around 14 volts.When the car is off, it should be around 12.If your readings are very off from this, you may have a bad battery. Noise. The noise that you hear when you try to start your car can tell you all you need to know.hen the car is off, it should be around 12. If your readings are very off from this, you may have a bad battery. Noise. The noise that you hear when you try to start your car can tell you all you need to know.