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How To Perform A Starter Solenoid Replacement (+ FAQs)

July 29, 2021

Do you suspect that something may be wrong with your starter solenoid? 

How exactly do you go about solving the issue

In this article, we’ll look at the steps involved in a starter solenoid replacement, provide the answers to some common starter solenoid questions, and even offer a reliable solution to your solenoid troubles

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Let’s dive in.

How To Perform A Starter Solenoid Replacement

If you think that you have a bad starter solenoid, you first need to decide if you’re comfortable performing the replacement yourself. 

Performing a replacement like this on your own is possible, but it will require some technical know-how and take a chunk of time. You’ll also need to ensure that you get the correct solenoid for your vehicle. 

If you’re not comfortable performing a starter replacement yourself, your best bet is to organize a reliable mechanic to handle the heavy lifting for you.  

To replace your starter solenoid, the mechanic will generally follow these steps:

Step 1: Park The Car On Solid Ground

The first step is parking the car on a solid surface. Many cars will need to be jacked up before accessing the starter solenoid. 

Step 2: Disconnect The Battery

Before starting any project on a vehicle, it’s a good idea to disconnect the negative battery cable. This will help avoid any shocks and can prevent damage to the car’s electrical system. 

The mechanic will locate the car battery in the engine compartment. 

From there, a socket wrench can loosen the attaching bolt to disconnect the battery cable and remove it from the negative terminal post. The red, positive cable won’t need to be disconnected from the battery terminal. 

Step 3: Locate The Solenoid

With the battery cable removed, it’s time to locate the starter solenoid. The thing to note here is that it can be in one of two places. 

The first is close to the starter inside the engine compartment. The mechanic can find the solenoid by following the red wire attached to the positive terminal of the car battery. In some cases, the red wire connects to the solenoid. 

If it’s not there, it’s connected to the starter motor, which the mechanic can usually find in the transmission’s bell housing, secured to the engine block. 

This makes repairing the solenoid a little more complicated as you’ll need to disconnect both the starter and the solenoid before removing it.

Step 4: Disconnect The Solenoid 

Before disconnecting the wires, the mechanic might note their locations to reconnect them quickly.

Most solenoids have three wires. 

One wire will be near the top of the solenoid, further away from the starter motor. There’ll be another wire near the bottom of the solenoid, and the final one is a wire pigtail that only connects in one place. 

The mechanic will disconnect this wire by pressing the release clip and pulling backward on the plastic harness. The other two wires should be held in place by bolts or screws. 

After having disconnected the solenoid wires, the mechanic removes each mounting bolt. The mechanic will then remove the starter motor from the engine compartment. 

If the mechanic can’t remove the solenoid from the car without the starter, separating the solenoid from the starter is usually a matter of removing a bolt or two.

Step 5: Compare The Old Solenoid With The New One

Before installing the new part, the mechanic needs to compare the old solenoid with the new one. While it’s a good idea to do this with every replacement, it’s more important with the solenoid.

The factory solenoid will likely have come with three terminals, whereas the new one might have four. If this is the case, the mechanic will connect the third wire to the terminal marked with an “S” and leave the other terminal.

The terminal marked with an “I” is for vehicles that use four wires as standard. 

If your car only uses three wires, a solenoid with four wires terminals will still work

Step 6: Install The New Solenoid

It’s time for them to connect the new solenoid to the original starter and mount it back in its housing, making sure to install each mounting bolt securely. The mechanic also needs to replace all the original shims. 

It’s also time to reconnect the car battery, ensuring the positive battery cable connects to the positive terminal on the battery, and the same with the negative. 

If there’s a noise when the engine is starting, it may result from some misaligned shims. Once installed, the mechanic will need to reconnect the car battery. 

Note: The mechanic will likely do a battery test before checking the solenoid. Without a full charge, the battery might struggle to initiate the starter.

Next, let’s take a look at some common solenoid questions. 

5 Starter Solenoid FAQs

Here are some common starter solenoid questions and their answers: 

1. What Is A Starter Solenoid?

A starter solenoid switch, commonly referred to as just a starter solenoid, is one of the main components of your car’s ignition system. Your starter motor wouldn’t work without it, as the solenoid essentially controls the battery voltage running to the starter motor. 

Essentially, without the starter solenoid, your engine wouldn’t have the power required to turn over. 

To identify the solenoid, first look for the starter. 

You can often find it near where the engine and the transmission connect. The starter is typically a cylinder with a smaller cylinder attached to it. The smaller cylinder is the solenoid.

Many people confuse the starter solenoid for the starter relay; however, the two are different parts. 

The starter relay is a small electrical device that activates the current required by the starter solenoid. The starter relay is basically a remote switch that controls a high-current circuit. 

However, the solenoid, together with the starter motor, gives your car the kick it needs to get going. 

Here’s a basic overview of how that happens: 

It’s the starter solenoid’s responsibility to power the starter motor. 

2. How Does A Starter Solenoid Function?

The starter solenoid’s process involves three basic stages: sucking, holding, and return:

From the sucking coil, the energy flows to the armature coil, rotating it at low speeds. The starter drive pinion is pushed out through this suction and engages with the ring gear while a plunger pushes in the contact plate, closing the main contact point.

At this point, the magnetic force formed by the holding coil and sucking coil neutralize each other, disconnecting the contact plate and stopping the starter.

3. What Causes A Starter Solenoid To Become Faulty?

Several factors can lead to a bad starter solenoid. Below are some of the more common causes: 

Melted starter solenoid contacts can also prevent the starter pinion gear from disengaging with the ring gear after startup. 

4. How Do I Know If It’s An Issue With The Solenoid Or The Starter?

The best way to determine which part is giving you trouble is to test your solenoid. 

Here are two ways you can test your starter solenoid:

A. Use A Test Light

Checking the solenoid (or a slave solenoid in a diesel engine) with a test light will give you the most accurate readings. If you don’t have one, you can pick one up for less than $20. 

To test your solenoid with a test light, follow these steps:

You should see two small terminals on the face of the solenoid. The top one is the 12 volt positive that connects to the battery. 

When activated, the lower solenoid terminal connects with the upper solenoid terminal, engaging the starter motor. If everything works properly, there should be continuous power going through the top terminal. 

To check, touch the red lead from the test light to the top solenoid terminal and hold it in place. 

To test the power, we need to complete the circuit by connecting the black lead to a grounded surface. You can touch it to the negative terminal on the battery to complete the circuit.

If the test light activates, it means there’s electricity flowing into the solenoid from the battery. This implies the battery voltage is okay, and the solenoid is the issue. 

Now you need to test if it’s transferring the power correctly. 

To do so, place the red lead on the lower terminal while keeping the black lead grounded. Remember, this terminal should only have power when the car’s on. 

With the leads still connected, have a friend turn the ignition. This should bridge the connections and send power to the lower terminal.

The solenoid is working correctly if the test light turns on. If the light comes on but the starter doesn’t, it indicates an issue with the starter and you may need a replacement. 

If there’s no light at all, you likely have a bad starter solenoid.

It may also be worth testing the battery to check for a voltage drop. Excessive voltage drop can cause motors to run hotter than usual and cause burnout. This may be amplifying the problems with your ignition system. 

B. Listen For A Click

If you don’t have a test light available, you can try this method to determine if the solenoid is working correctly. Before getting started, you’ll need another pair of hands. 

5. What Should I Do If My Solenoid Is Faulty?

If you leave a bad starter for long enough, eventually, your car won’t start at all. 

If you’ve determined a bad starter solenoid is the root of the issue, you could try to jumpstart your car with a pair of jumper cables and try to pick up a rebuilt starter. 

Of course, this would mean installing the part yourself. 

Bear in mind that this option is more challenging than replacing a starter solenoid in a mower or riding mower. As such, you’ll need a good amount of technical knowledge.

Instead, your best bet would be to arrange for a reliable mechanic to come to your driveway to take a look. This avoids any unnecessary risks and removes all the hassle. 

For this, you can rely on RepairSmith!

RepairSmith is a convenient mobile auto maintenance and repair service. 

Here’s what they offer: 

For an accurate cost estimate, simply fill out this form

Wrapping Up

Several things can cause your solenoid to start malfunctioning. If you suspect yours is playing up, it’s possible to install a replacement yourself. 

However, performing a starter replacement is a complicated and time-consuming job. 

If you’re unsure which solenoid will fit your car or would rather just avoid the hassle, consider letting the professionals handle it for you. 

Just rely on RepairSmith when you suspect that you have a bad starter solenoid! Just contact them and let their ASE-certified technicians come to your driveway to do the heavy lifting.