While it might sound like a bit of alien tech, a starter solenoid is a common component of modern vehicle ignition systems. Starter solenoids are reliable, often lasting 100,000-150,000 miles before showing any problematic symptoms.
How do you know if your starter solenoid is bad? If the engine struggles during startup or doesn’t crank at all, the solenoid may be going bad/have failed.
Listen for clicking sounds when turning the key or continued grinding/whining after the engine starts, both of which suggest starter solenoid problems.
Below, we’ll explore the symptoms of a bad starter solenoid in greater detail. But first, let’s look at how the starter solenoid works and where to find it.
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What Is A Starter Solenoid, And How Does It Work?
Simply put, a car’s starter solenoid is a device that relays power from the battery to the starter motor. For more details on the exact process, read on. Otherwise, skip to the next section to learn where the solenoid is located.
Inside a solenoid is an iron piston that can move forward and backward. The piston has copper wire coiled around one end and a spring on the other.
As electricity from the battery flows through the solenoid’s copper wiring, it becomes energized, creating an electromagnetic field that attracts the metal piston and pulls it back. This also compresses the spring, which returns the piston to its original location once the solenoid de-energizes.
With the piston pulled back, an electrical circuit is closed that allows power to reach the starter motor and, in turn, turn the flywheel that cranks the engine. Once the engine starts, the circuit opens again, the piston returns, and electricity stops flowing.
Prefer a visual example? Be sure to check out the below video from TecknoMechanics:
Where Is The Starter Solenoid Located?
The starter solenoid is cylinder shaped and is often mounted to or built into the starter motor. The motor’s location varies between models, and you may need a flashlight, but it’s usually under the transmission or under the exhaust or intake manifold.
You can also follow the battery’s positive terminal to the starter solenoid, though, depending on the vehicle, you may need to remove the battery and tray to reach it.
Look for a couple of electrical connection points coming out of the back of the solenoid. One leads to the battery’s positive terminal and another to the starter motor. A third smaller point connects to the ignition cylinder and conveys when the key is being turned.
5 Signs Of A Bad Starter Solenoid
What causes a starter solenoid to go bad? General wear and tear associated with age is the main cause of a bad solenoid. This includes prolonged exposure to the heat created by the motor (and/or extreme climates), moisture entering the engine bay, or worn, corroded wiring.
Parking in a garage and giving the engine a rest during long drives can help reduce potential heat damage. To minimize water intrusion and protect against electrical shorts and corrosion, be sure to keep the vehicle’s drainage lines clear of obstruction and avoid driving through large puddles.
Simple maintenance hacks like these are great for extending the life of a vehicle. Be sure to check out our previous article for more car maintenance tips.
1. Rapid Clicking When Turning Ignition Key
If turning the ignition key results in rapid clicking sounds, the starter solenoid may not be getting enough electrical current to turn the flywheel and engage the crankshaft.
Before replacing the solenoid, though, be sure to have it checked (or check it yourself with a multimeter), as a dead battery can cause similar symptoms.
2. Starter Motor Stays On After Engine Starts
A starter motor makes a distinct grinding/whining noise when cranking an engine over, but only for a moment. Once the engine is running, the starter should shut off. But, if the solenoid has failed, the starter may continue spinning.
Ignoring this problem can lead to the starter itself needing to be replaced, which is much costlier than just the solenoid.
3. Nothing Happens When Attempting Startup
Cars typically click when you turn the ignition key, and starters make a grinding noise. However, if nothing happens, the solenoid may be the culprit.
Pay close attention to the electronics inside the vehicle. If the radio and lights turn on, as usual, the solenoid is likely at fault. But if nothing works or lights up, the issue may stem from a dead battery.
4. Starter Motor Cranks But Engine Does Not
You may need a new solenoid if you hear the starter motor spin but the engine doesn’t attempt to turn over. This typically happens for the same reason as other symptoms on this list; the starter isn’t receiving enough power to rotate the crankshaft.
Testing the solenoid will tell you if you need a new one, but you may find the starter itself is the issue or that you need to replace the battery.
5. Engine Starts Only Some Of The Time
Another sign of a starter solenoid that’s beginning to go bad is the engine only starting occasionally. This indicates the solenoid is on its last legs and may fail soon entirely. You may also notice some of the other bad solenoid symptoms on this list.
Think Your Starter Solenoid Is Bad? Here’s What To Do
If you think your starter solenoid is bad, the first step is to test it, as there are many reasons a car might not start. You can either take your car to a shop for a fee or use a multimeter to test it at home.
Not sure how to test a starter solenoid? Check out the below YouTube video from TutoBuild Eng for a step-by-step visual explanation:
Should the starter solenoid be at fault, you can either take it to a mechanic or, if you’re marginally handy with an engine, swap it out yourself.
The solenoid’s exact location differs between models, but the below video from Thinking Outside Box does a nice job of explaining the basics:
What happens if you ignore a bad starter solenoid? Eventually, you won’t be able to start your car. Instead of leaving it up to chance, be sure to test the starter solenoid as soon as symptoms appear.