At first glance, the ignition switch might seem like a simple mechanism. Nonetheless, it plays a vital role in a vehicle’s function. And when you have to replace or repair this auto part, you will realize how complicated it can be. One of the things that confuse motorheads the most is the ignition switch wiring color code. In this article, DriveRevolve will walk you through every step of wiring the ignition switch and explain what color goes to what. In addition, we will investigate whether or not this part of your car needs to be grounded. So read on, and by the time you’ve finished reading, you will become an ignition switch wiring expert! 

What’s An Ignition Switch In A Car? 

Before we begin, let’s get you familiar with the ignition switch. The system is made up of several components working together under the control of the car’s internal computer. Aside from starting the engine, it also provides power to other electronic accessories. Since the ignition switch grants initial access to vehicular power, keeping this part in good condition is crucial for your car’s lifespan. 

Ignition Switch
A lot is going on within this tiny auto part – Source: American Autowire

Starting with the ignition coil, the ignition switch converts energy from the battery into powerful sparks. That’s how it ignites fuel vapor. The coil itself consists of a primary and a secondary winding. While the primary winding is responsible for amassing the power required to generate a spark, the secondary one delivers that power to the distributor.

With the help of a rotor, the distributor transfers the sparks to the spark plugs through wires. These spark plugs are connected to the cylinder head. As the intake valves ensure the amount of vapor and fuel in the cylinder, the spark plug will release a hot spark that ignition, resulting in combustion. 

General Ignition Switch Wiring Color Code 

Car ignition switch wiring color code

As crucial as it is, your ignition switch can fail sometimes. When you have to diagnose and fix the problem with this vital car part, the ignition switch wiring color code will come in handy: 

RedBattery in
BlackIgnition out
Red/black (thick)Radio supply
Red/black (thin) Power into key-in switch

Aside from the colors, what wires go to ignition switch is also a frequently asked questions on Car Talk Community. The most common guide is as follows: 

  • ACC: Accessory 
  • BATT: Battery+ 
  • IGN: Ignition
  • ST: Start signal 
Ignition Switch Wiring Color Code
An example of 4 wire ignition switch diagram – Source: PNGWing

This setup is the standard for most car models, but if you own a modern vehicle, it might be different. For this reason, it is best to check out the service manual before working on your ignition switch. That way, you will understand all the terminals your ignition switch has. Keep in mind that any mistake with the wiring can severely damage your electronic parts, so do careful research before the repair is required. 

How To Wire An Ignition Switch? A Step-By-Step Guide 

Now that you’ve got the ignition switch wiring color code, it’s time to begin the wiring process. 

The process consists of 7 steps and can be completed in less than an hour. Since it is relatively easy, you can perform it at home without the help of a licensed mechanic. Knowing the position of each wire is the only thing that matters, so if you still don’t remember, go through the manual once again before jumping into this DIY project! 

Step 1: Prepare The Car

Before beginning any at-home job on your car, it is essential to get everything ready in advance. Thus, the first step is to gather all the necessary equipment and tools. Otherwise, you will just waste time searching for parts when you are in the middle of the task. 

Prepare The Car
Get your car parked on level ground before wiring the ignition switch – Source:

What’s more, you should park the car on level ground. Make sure that the emergency brake is engaged. As you continue the procedures, the engine must be shut down. 

Step 2: Disconnect The Battery 

The next thing to do is to disconnect the battery. Observing the battery, you can see two sides: negative and positive. 

Use a small wrench or socket to loosen the bold and disconnect the negative side. Keep it from making touch with the positive terminal while it is detached. 

Step 3: Identify The Terminals On The Ignition Switch 

This is the most critical step. As mentioned, an ignition switch often has 4 terminals: ACC, BATT, IGN, and ST. Your job is to find out and identify them. 

Identifying ignition switch terminals

Depending on which car you drive, these terminals can have varying marks. They might be numbers or letters, and I’d recommend referring to the car’s repair handbook to make sure that you got all the terminals correctly. If necessary, check out a 4 wire ignition switch diagram for your specific model of the ignition switch. 

Step 4: Take Off The Protective Cover From The Steering Wheel. 

Now, look at the steering wheel. If you see any plastic trim attached to it, take off these pieces. For this task, you will disassemble some plastic clips and connectors that keep the trip in place. As you remove them, store the clips, screws, and bolts in a safe location, and don’t forget where they belong. 

Steering Wheel.
Taking off the protective cover from the steering wheel will make it easier to complete the procedure – Source: Amazon

The removal of the steering wheel will make the procedure much easier for you. If taking it off is too troublesome, using a puller can make it a bit easier. To avoid damaging anything part, be sure to follow the procedure outlined in your car’s service handbook.

Step 5: Connect The Wires 

Find the positive lead from the vehicle’s battery to the ignition switch. In most cases, it is a thick red wire that’s continuously powered. Insert the terminal end into the power lead wire and make sure it’s secure. Join the wire to the switch’s BATT terminal so it can receive power. 

Next, attach the auxiliary wire to the ACC terminal when the ignition switch is in the accessory (ACC) position. This wire will supply electricity to various accessories of the vehicle. 

Establish the connection between the starter relay wire, which is right beside the ST terminal. This terminal only receives power when the ignition switch is set to the Start position. 

The last connection should be made between the IGN terminal and the ignition wire. This is the main control terminal that operates the ignition as well as the accessories, wipers, and other functions. It’s the same thing as having the switch set to the Run position.

How to connect the ignition switch wires

Step 6: Reassemble In Reverse Order

Now that you are done wired everything, it’s time to put the switch back in place. To do this, you will need to press down on the pin. Place the ignition switch back into the steering column with caution, and try not to break any fragile components. 

Then, get everything back in order. Pay attention to the shape of the master cylinder, the ignition module grooves, and the release position of the pin. When you are done setting up the ignition switch, you should hear a clicking sound from the pin. Keep pressing on it until you hear this clicking noise.

Step 7: Test Your Work 

The final step is double-checking your work. Completing this step requires reconnecting the battery. Nonetheless, aside from the battery, other parts don’t have to be put back in place yet. You will want to keep them disassembled in case you need to fix something else. If the process goes smoothly, you should be able to turn the ignition and notice that your car’s function is back to normal. If not, you have to review the instructions again and determine what went wrong. 

Final step
If your car is back in service, you’ve done a good job – Source: U.S. News Cars

Once you know that the ignition switch is functioning normally, move on to reassembling the remaining parts. Shut down the engine and disconnect the battery again for your own safety. If you forget the place of a certain part, you can refer to the service handbook. It’s crucial to put everything back where they come from. 

Does The Ignition Switch Need To Be Grounded? 

If you have some knowledge about connections, you will know the importance of the ground. The ignition switch, on the other hand, doesn’t function in the same way. There is no connection between the terminals and the ground, and since they are separated, each of them can carry out a particular mechanical duty with ease. 

Due to this, grounding the ignition switch is unnecessary if you want to start the car. 

Frequently Asked Questions

What Are Some Symptoms Of A Bad Ignition Switch? 

Symptoms of a bad ignition switch include engine shaking and loss of power, intermittent loss of lighting and other electrical accessories, tire pressure sensor fault, and difficulty turning the key.
When you notice one or more of these issues, it’s time to get your ignition switch checked. 

Can You Bypass An Ignition Switch To Start A Vehicle? 

Yes, it is possible.
By connecting the BATT wire directly to the battery, you can start the engine without using the ignition switch. However, modern models include immobilizers that prevent such action. 

Do You Need A New Key When You Replace The Ignition Switch? 

In most cases, it is not necessary. To replace the ignition switch on a modern car, you can order one without having to get a new key. 

How to start a car without using an ignition switch?

Wrapping Up 

All in all, understanding the ignition switch wiring color code ​​and the necessary steps to wire one will help you a lot when dealing with this auto part. An auto repair shop might charge you a fortune to find out and repair the issue, but with our guide, you can turn it into a DIY project and save your wallet! 

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