Rapid clicking noise when trying to start engine
If you turn the key and all you hear is rapid clicking when trying to start engine, that’s the sign of a dead battery or corroded battery terminals. Here’s the sound.
What causes rapid clicking noise?
Every starter has two main components: the starter motor and the solenoid. The starter solenoid does two things: 1. Pulls in a plunger that pushes a disc against two electrical contacts to complete the flow of power from the battery to the starter motor. 2) Moves a shift lever to force the pinion gear to mesh with the flywheel gear.
If the battery is discharged or the battery terminals are corroded and have high resistance, the solenoid can’t work properly. It pulls in and tries to move the pinion gear into position, but the low power causes it to bounce back. That’s what’s making the rapid clicking noise.
How the starter solenoid works
The starter solenoid has two windings, a “pull-in” coil and a “hold-in” coil. The pull-in coil generates enough magnetic field to get the plunger moving, but it’s not strong enough to hold the plunger in place against the force of the return spring. That’s the job of the hold-in coil.
The hold-in coil requires must far more electrical power to generate a large enough magnetic field to hold the plunger firmly against the relay disc.
If your battery is discharged or the battery terminals/posts are corroded, there may be enough power to pull-in the plunger, but not enough power to hold it in place. When that happens, the plunger gets pulled in and then immediately bounces back, repeating the movement over and over, which is what causes the rapid “machine-gun-like” sound you heard above.
How to stop the rapid clicking noise and get your car started
Start by removing and cleaning the battery terminals and battery posts . See this post for detailed instructions on how to clean terminals and posts.Then try starting the engine. If it starts, drive it at highway speeds for at least 20-30 minutes to recharge your battery
If cleaning the terminals and posts doesn’t help, have your battery tested.
Why the rapid clicking noise happens most often in Spring and Fall
Ambient temperatures swing wildly in late Fall and Spring. It’s not uncommon to have a 55° day with a temperature drop down to the ’20s at night. The battery posts and terminals expand and contract with the extreme temperature changes and lose their solid electrical contact. So you can get rapid clicking first thing in the morning when everything is cold and then later in the when things heat up and expand, it starts just fine.
Second, all batteries produce less power when cold. A weak battery may not be able to provide enough power to fully operate the hold-in coil. So test the battery to determine its state-of-charge. If the battery tests good, clean the battery posts and terminals. If that doesn’t fix the problem, test the battery.
Why a jump start doesn’t always work
People wonder why jumper cables don’t help if the terminals are corroded. Simple, you apply power to the positive terminal but you’re still not getting a complete circuit at the negative terminal to the ground.
©, 2020 Rick Muscoplat
Posted on by Rick Muscoplat