Most cars have four wires that go to the ignition switch for the ignition input, start, battery, and accessory. As such, you'll find that your ignition switch generally has four terminals with wire connections.

If your ignition switch fails, an auto repair shop might charge you a pretty penny to diagnose and fix the issue. However, you could also make it a DIY project to save money.

If you want to learn what wires go to the ignition switch and how to replace it yourself,

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What wires go to the ignition switch?

If you own a modern car, it most likely has a 4-wire ignition switch. These switches typically have four terminals with the labels:

BATT (battery). A thick red wire that is always energized usually connects here.

IGN (ignition input). This is the primary terminal that controls your vehicle's ignition and other electronics. It may be connected with a yellow or red wire.

ST (starter). This terminal connects to the starter solenoid. It may have a brown or yellow wire.

ACC (accessory). This terminal sends power to the accessories on your car, such as the lights, radio, and windshield wipers. It usually has a purple wire.

If you're planning to replace your ignition switch or simply want to disassemble the steering column to do some troubleshooting, you need to pay attention to what wires go to the ignition switch.

The wire colors listed above may vary depending on your car's make and model, so it's important to go based on where the wires should be connected. The BATT wire will almost always be red, but you may find other colors, like white, green, and black, for the other three.

Consult your owner’s manual if you have any confusion about which wires are which.

MORE: Ignition switch replacement cost

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A step-by-step guide to wiring an ignition switch

You may be dealing with a faulty ignition switch if you see any of the following issues:

Failure to start (this can be the result of many different problems and is only one symptom of a bad ignition switch)

Your

car stalls

or shakes while driving

Interior accessories, like dashboard lights, flickering or not working

The key won't turn or gets stuck in one position

The ignition stays on even after removing the key

Luckily, wiring an ignition switch isn't too complex with the right know-how. You can complete it in your driveway or garage using the following steps.

Park your car

The first step is to ensure that you park your car in a safe and level spot to work.

Figure out the terminals on the ignition switch

There are four terminals on the back of the ignition switch: BATT, IGN, ST, and ACC. Locate and identify these terminals.

Depending on your car's make and model and the ignition switch brand, these terminals may be marked using slightly different letters or numbers. It's always a good idea to consult your vehicle's repair manual and the ignition switch manufacturer to ensure that you correctly identify the four terminals.

If necessary, consult an ignition switch wiring diagram for your vehicle to be sure of the terminals' labels.

MORE: Ignition coil replacement cost

Disconnect the battery terminals

Open the hood of your vehicle and, using a small wrench or ratchet and socket to loosen the bolt, disconnect the car battery's negative (-) terminal.

Take off the steering wheel trims

Remove any plastic trim pieces attached to the steering wheel. To accomplish this, you might have to pop out several plastic pins and connectors. Set these items to the side and remember where they belong.

Take apart the steering wheel

Although it isn't necessary for all vehicles, removing the steering wheel will free up space and make everything else easier. You may need to use a steering wheel puller to remove the steering column.

It's a good idea to consult your car's repair manual before starting this step, as you could potentially trigger the airbag or warning lights.

MORE:

How to start a stalled car

Take off the ignition module cover

Remove the plastic cover surrounding the ignition module. You may have to use a screwdriver to release the plastic clips holding it together.

Press the release points on the clips with the screwdriver and slide the ignition module cover off. Set it safely aside for later.

Put the keys in the correct position

Place the car key in the ignition and turn it to the ACC (accessory) position. This is necessary to press the release pin so you can remove the ignition switch from the module.

If you don't have your car's ignition key, you might be able to accomplish this step using a flathead screwdriver—just be careful not to damage the ignition barrel slots.

Release the pins

If you've completed every step correctly up to this point, the ignition switch should slide free when you turn the key to the ACC position.

Examine the ignition switch

Carefully remove and examine the ignition switch. If you want to use the same keys, you'll need to have your existing ignition switch rebuilt. Otherwise, you can simply purchase and install a new ignition switch that meets your car's requirements.

Look at your wires

Locate the positive (+) power lead that connects your car's battery to the ignition switch. It is usually a thick red wire.

Once you locate it, use a terminal multi-tool to connect the wire to the BATT terminal on the ignition switch.

MORE: Why isn't my car starting? A quick troubleshooting guide

Attach the accessory wire

Connect the accessory lead wire to the terminal labeled ACC on the ignition switch. This is the wire that controls your vehicle's accessories when the key is in the ACC position.

Attach the starter relay wire

Connect the starter relay wire to the ST terminal on the ignition switch. This wire connects to your car's starter solenoid and activates when the key is in the "START" position.

Connect the ignition wire

Finally, attach the ignition wire to the IGN terminal of the ignition switch. This terminal controls the car's ignition and other electrical features and is essentially its "run" position.

Replace the ignition switch

Reinstall the new or rebuilt ignition switch by lining up the cylinder and sliding it into place. You may need to press down the release pin slightly. Once you hear the click of the release pin, you'll know the switch is correctly seated in the cylinder.

Test the ignition switch

You need to reconnect your car's battery to test your ignition switch. Don't bother reassembling the steering wheel column yet in case the switch doesn't work.

Once you've reconnected the battery, insert the key into the ignition and try to start the car. If everything is working properly, the key should turn smoothly, and the engine should start with no issues.

If the key sticks or is hard to turn, or if the vehicle doesn't start, you'll need to work backward to troubleshoot and locate the issue.

Put the car parts back together

If everything is working properly, you're ready to put your car back together. First, turn off the engine and disconnect the battery again.

Then, reassemble the car parts in exactly the same way you found them. If you can't remember where a part goes, consult your repair manual or try to find the answer online.

Key Takeaway There are four wires connected to the back of the ignition switch labeled BATT, IGN, ST, and ACC. To access your ignition switch, you'll need to take apart your steering wheel and remove the ignition module.

What does the ignition switch do?

The ignition switch is an important part of your car's ignition and electrical systems.

The ignition system in your car generates between 20 and 30 thousand volts of energy, which is required to ignite the fuel in the engine. The ignition switch directs the power from the vehicle's 12-volt battery to the starter solenoid and the car's accessories.

MORE:

What is that grinding noise when I start my car?

How to find affordable car insurance

A working ignition switch is imperative to keeping your car running. But without a quality

car insurance

policy, your vehicle is left running without protection.

You could spend hours online searching and comparing various companies and their policies to find the right fit—or you could let

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MORE: Symptoms of a bad car starter

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FAQs

What color wires go to the ignition switch?

Generally, the positive power lead will be a thick red wire. The remaining wire colors may vary depending on the vehicle but are usually green, blue, yellow, black, or white.

What wire goes from the ignition switch to the starter?

The ST (START) wire goes from the ignition switch to the starter.

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