How does a hammer fix a starter?

In this series of Q&A posts we are using google’s autocomplete function to find the most commonly asked questions about cars and giving them each a definitive answer. This week we answer the question “how does a hammer fix a broken starter?”

You may have heard of this little trick before. If you know the symptoms of a bad starter, you can shock your vehicle back to life long enough to get to a mechanic by giving your starter a tap with a hammer or solid metal object.*  Starter motor problems usually have the same symptoms: Turn the key to start your vehicle and you hear a loud click, or sometimes you hear nothing. The headlights are bright and don’t dim when you turn the key, and everything else electrical seems to work fine. This tells you it could be a bad starter neutral switch or a bad key switch but about 99% of the time it’s a bad starter or starter solenoid.

How does the starter work?

When you turn the ignition key to the START position, the battery voltage goes through the starter control circuit and activates the starter solenoid, which in turn energizes the starter motor. At the same time, the starter solenoid pushes the starter gear forward to mesh it with the engine flywheel (flex-plate in an automatic transmission). The flywheel is attached to the engine crankshaft. The starter motor spins, turning over the engine crankshaft allowing the engine to start.

How does this temporary fix work?

A starter is essentially an electric motor with graphite brushes inside, and over time, they wear out. If a little moisture gets in the housing and rusts up the brushes and brush holders, or the brushes are nearly worn out, gently rapping on the starter housing can sometimes free them up, letting them make enough contact to make the starter work. That’s all tapping will do, it is not a magic formula to fix anything long term, but this temporary measure will help to get you home or to the mechanic. If tapping on the unit doesn’t offer instant results then there are other problems and all the hammering in the world will not make it work.

Need help?

Having trouble getting your car started? If you unsure if you need a tow or might be able to get it started on your own, give us a call, we’d be happy to help.

*Special Note

Inside some starters are permanent magnets instead of electrically energized ones as in the days of old. A hard whack or use of aggressive force could crack the magnets and then a whole new starter would be required. Using a medium weighted tap is more than enough, as it doesn’t take an extraordinary amount of force to jar the brushes to contact the commutator. If you do not have a hammer handy, if you are away from home, use a heavy metal object like the tire iron in your car to give it a little tap. It just might save you the cost of a tow.