How do you know if your starter in your car is bad?

If the engine will not turn over then either the battery, starter, or ignition switch is bad. Turn on your headlights and have someone try to start the engine. If the lights go almost completely out then the battery is more than likely bad. If the lights just dim then the battery is probably good. Another way to check the charge of the battery is with a Digital volt meter. A fully charged battery will read 12.6 volts DC on the volt meter set to the 20 volt scale. If you do not see the light dim or go almost out, and hear a click, then the ignition switch is more than likely the culprit. This is assuming the main fuse is not blown. The only way to check the starter 100% is to remove it and have it bench tested at any auto parts store.