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What is a Starter Solenoid?
On older cars with the starter solenoid mounted on the firewall rather than the starter motor itself, the solenoid is essentially a relay. When it receives a signal from the ignition switch, it closes the circuit and sends a powerful current to the starter motor so it can crank the engine over. However, this design is pretty rare these days.
On virtually all cars manufactured in the past 40 to 50 years, the starter solenoid is integrated onto the starter motor – it looks like a smaller cylinder on top of the starter assembly where the electrical connections attach. It also acts as a relay to close the circuit to the starter, but it does much more.
When the solenoid gets an ignition signal, an electromagnet pulls a plunger back in the solenoid. That motion moves a shift lever that pushes the drive pinion on the starter motor outward so that the pinion gear is inline with the flywheel’s ring gear.
Meanwhile, the powerful current from the battery bridges from the solenoid to the starter motor and causes the electric motor to rotate, spinning the engine over.
When the ignition is released, power is immediately disconnected at the solenoid. The starter stops spinning under power and freewheels to a stop while the solenoid plunger moves back to its resting position, letting the pinion gear release from the ring gear.
Causes of a Bad Starter Solenoid
Over time and with use, bad starter solenoid symptoms can develop. It can occur from a few different origins, and some are much more prevalent than others. Causes include:
- Corrosion. It can occur around the terminals due to moisture and oxidation, creating poor electrical contact and preventing the starter motor from engaging.
- Broken connections. Another common cause of bad starter solenoids is a loose or damaged connection. Over time, internal connections can come apart because of vibrations while driving or extreme temperatures.
- Wear and tear. Some starter solenoids simply become too old or worn out due to daily use over many years and need to be replaced in order for the car to start properly.
Signs of a Bad Starter Solenoid
When a starter solenoid isn’t working as it should, you’ll encounter symptoms that point you to it. One of the first and most common symptoms is simply no response from the starter when you turn the key – no noises or engine cranking at all. Sometimes, repeatedly trying the ignition can produce a result, but that’s not guaranteed. It usually means there’s a faulty connection in the solenoid.
Another common symptom is a single clicking noise when you turn the key. It indicates that the solenoid is receiving the ignition signal but there’s an internal connection issue or binding that’s preventing the starter from engaging.
Grinding noises are a common occurrence for a bad starter solenoid. The starter is cranking over but the solenoid isn’t pulling the shift lever back properly to engage the pinion gear with the flywheel, and the gears are grinding against each other.
Finally, it’s possible for the starter to remain engaged after the ignition input has stopped. A short inside the solenoid causes power to constantly bridge to the starter when the ignition is in the on position.
Preventing Starter Solenoid Problems
The starter motor and its solenoid are installed in an area that’s rather inhospitable with high heat and environmental elements constantly bombarding it. There’s not much that can be done to protect the starter solenoid from exposure, but there are ways to prevent abnormal wear or corrosion.
You should keep the solenoid terminals free of dirt and debris, as this can cause corrosion and lead to failure. It’s also important to check the wiring between the ignition switch and the starter motor to make sure that there are no loose connections, which can cause too much current to be sent to the solenoid. Following these steps can help extend the life of the starter solenoid and avoid costly repairs in the future.
If your starter solenoid fails, find a replacement from well-known brands at AutoZone store near you. Source all the parts you need to keep your car running – and starting – at its best, and get Trustworthy Advice from our associates. If the job is too big for you, seek out one of our Preferred Shops to help you do the job.
FAQ/People Also Ask
What is a starter solenoid?
The starter solenoid is an electromagnetic switch that engages the starter motor.
How can I tell if my starter solenoid is bad?
If you’re having trouble cranking the engine over but the battery is charged, or if your starter won’t disengage after starting the engine, it’s likely a starter solenoid issue.
What causes a starter solenoid to go bad?
Often, a combination of corrosion, heat, and wear and tear cause the starter solenoid to fail.
Can a bad starter solenoid drain the battery?
It’s possible. If the solenoid won’t disengage, the constant current from the battery can discharge it.
Is it dangerous to drive with a bad starter solenoid?
If you drive with a bad starter solenoid, you could be stranded when you turn the engine off.
