Rick's Free Auto Repair Advice

Car makes clicking noise when trying to start

Car makes clicking noise when trying to start

If all you hear is rapid clicking when trying to start car, that’s the sign of a dead battery or corroded battery terminals. Here’s the sound.

What causes clicking noise?

The starter solenoid does two things: 1. Pulls in a plunger that pushes the relay disc against electrical contacts that 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.

The starter solenoid has two coil windings

The starter solenoid has two windings, a “pull-in” car won't startcoil 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.

Discharged battery or corroded terminals reduce power to the hold-in coil

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.

Car makes clicking noise when trying to start — this happens most often in Spring and Fall

That statement sounds weird, but there’s actually a method to the madness. First, 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.


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Posted on by Rick Muscoplat

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