Often, a poor connection at one of the battery cables can cause the starter motor not to work. The positive cable connects the positive " +" battery terminal to the starter solenoid. The negative (ground) cable connects the negative " -" battery terminal to the engine cylinder block, or transmission, close to the starter. That's why it's connected to the battery with thick (large gauge) cables (see the diagram). Of course, this could also be caused by damaged teeth on the ring gear of the flex plate or flywheel.Īs we mentioned, the starter motor requires very high electric current to turn over the engine. Often, this might cause a loud screeching noise when starting the car. The starter motor doesn't run, even though there is a 12-Volt power at the starter control terminal.Īnother symptom is when the starter motor runs, but fails to turn over the engine. What are the symptoms of a bad starter motor: When starting a car with a fully charged battery, there is a single click or nothing happens at all. If the battery is discharged, the lights in a car might work, but it won't be enough power (current) to turn over the starter motor. To turn over the engine, the starter motor requires high electric current, which means the battery has to have sufficient power. The starter motor is powered by the car's main 12-volt battery. See how the starter motor works inside below. In most cars, the starter motor is bolted to the engine or transmission, check these photos: photo 1, photo 2.