How To Wire a Starter Switch: An Ultimate Guide On Ignition Switch Wiring?


As you enter your car and sit in the driver’s seat of your vehicle, first, you turn the key over, hear a rumbling sound, and are ready to go. Turning the key is a reliable and easy process of starting an engine in today’s motor vehicles. So, how does the Ignition switch work? You can get it if you know how to wire a starter switch

Table of Contents

How To Wire a Starter Switch: What is an Ignition Switch?

You can also call it the “starter switch, ” which helps start the engine. 

Usually, you can see the switch in two ways: turning over a key in the slot and pushing a start button (as in most modern vehicles).

The ignition switch works as a trigger for your car’s engine. When you activate this switch, all your car’s electronic accessories and electrical devices get started as the current from the battery reaches all these devices. In other words, the ignition switch works as an intersection between your car’s starter and battery. Also, it works as a mediator between all the car gadgets, be it power windows, radio, air conditioning, etc., and the battery. 

But why do we need a junction between the battery and the car’s accessories? Why don’t we create a direct connection with the battery? There are two reasons for this. First, the direct contact would have drained your battery very quickly. Secondly, you would be unable to control when you want to start the electronics and electrical accessories. 

Ignition switch wiring diagram 

Caption: Ignition switch wiring diagram 


Different parts of an ignition switch

There are two distinct parts of an ignition system. Though they all have different operations, many people use them interchangeably. However, if you can differentiate between these two, you can fix the Ignition properly. 

How To Wire a Starter Switch: Lock cylinder:

The part that comes out of the dashboard or the steering column, where you insert the key and twist it, is the lock cylinder. These cylinders are becoming extinct as cars get a wireless signal. You only have to press the button to boot up the engine.


The ignition switch (electronically controlled) lies within the dashboard or the steering column. The controller sends the electronic signals to the car’s computer, which contains your car’s ignition system. 

In some cars, the switch and lock cylinder come in a single unit; in others, they are split apart.

An example of an ignition switch wiring harness

Caption: An example of an ignition switch wiring harness

The Position of the Ignition Switch

There are four positions in the lock cylinder. These are OFF (most anti-clockwise), ON or RUN, and START (most clockwise). Apart from this, an extra switch can work when you push the key inwards, and this is PRIME or CHOKE. With this push switch, you can control a priming circuit that helps start the engine, while the rotating button helps prevent the starter and the engine motor.

ignition starter switch key operated inners

ignition starter switch key operated inners

How To Wire a Starter Switch: Ignition switch wiring

If you look into the ignition lock cylinder, you will notice some letters. These letters denote different states of turning the ignition switch. The critical locks in all the forms and functions according to the markings. The terminal identifiers of the button follow a historical marking, and the color coding on the conductors helps identify their position. 

Though cars have different labeling, generally, you will notice four pins as follow:

BATT: a battery that connects the ignition switch to the car’s battery (12 Volts)

ST: It means a starter pin that connects to the starter solenoid. After contact, it is spring-loaded.

IGN: Ignition pin, the default ignition point for the vehicle’s Ignition, electrical accessories, and other devices.

ACC: an accessory that connects and powers all the car’s accessories like lights, radio, etc.

Note: in some old cars, you may join the choke and individual wires to Magneto apart from these connections.

How To Wire a Starter Switch: 4 positions universal ignition switch wiring diagram

Caption: 4 positions universal ignition switch wiring diagram


When you rotate or push the switch, the arrangement of the wire contacts brings the following connections.

First Position: When You Insert the Key into The Slot

How To Wire a Starter Switch: : Pictorial view of rear of ignition switch showing terminals and legends


It is position 0 or LOCK or OFF. This position is only to insert the key safely in the slot, bringing no change to the car’s ignition system or electronics. Only when you turn it clockwise will the Ignition start. When you stop the car, get the key back in this LOCK position; otherwise, the key will not come out of the slot. It mainly works as a safety feature.

The switch has two M terminals that connect only to the OFF position. With these terminals, you can join the ignition kill circuit or the Magneto to the ground. The lower M terminal connects to the negative battery or ground terminals (black). The raised M terminal connects to the Ignition kill circuit, i.e., black with a yellow stripe. As the engine wire carries a high voltage of around 300 volts, it is essential to observe the connections. 

The circuit goes to the raised terminal, which isolates it from all other connections. You can also use the M terminal as a wiring point to connect another switch in a parallel connection. You can operate this second switch through a safety lanyard. When you run the second switch, the two M terminals connect and kill the engine even if the button is not in the OFF position. 

Second Position: When You Let Your Internal Car Accessories Power On

How To Wire a Starter Switch: : Pictorial view of rear of ignition switch showing terminals and legends


It is the position I, the “ACCESSORY” or the “ARC.” In this position, you connect the battery with the internal accessories of the car while keeping the engine off. The car’s comfort that you can enjoy in this position includes a radio, power windows, multimedia, lights, heated seats, and others that require electricity to work. However, please don’t leave the keys in this position for too long as it drains the battery.

Here, the B terminal of the battery (12-Volt power) connects to the A or I terminal and supplies the voltage of the accessory loads. It is a RUN or ON position.

Third Position: When You Prepare Your Car’s Ignition System To Start

How To Wire a Starter Switch: : Pictorial view of rear of ignition switch showing terminals and legends


It is position II or ON or IGNITION. In this ON part, all-ethe electric systems of your car turn on. It includes all accessories and the engine itself. It will also turn on the fuel pump to circulate diesel or gasoline to the engine. In this default state of the switch, you cannot remove the key.

When the rotating switch is in the ON or START position, the push switch connects the B and C terminals so that voltage from the battery reaches the engine primer circuit. Also, the B terminal connects to the A or I terminal in RUN, and the A terminal to the S terminal in the START position. 

Fourth Position- When You Crank The Engine, Turn Over

How To Wire a Starter Switch: : Pictorial view of rear of ignition switch showing terminals and legends


It is position III or START position. It’s the time when you are ready to go. You will hold and twist the key in the START position so the engine’s cranking starts. With this, your car starter plays its role and induces high voltage to ignite the engine. Once the motor starts running, the key will return to the ON position, turning off the engine.

Here, the B terminal connects to the A and the S terminals and supplies battery voltage to the engine, engine starter solenoid, and car accessories. It is the START position. 

How To Wire a Starter Switch: Signs of a Faulty Ignition Switch

Several signs indicate that your ignition switch has some fault.

Your car doesn’t start:

When you turn on the key, and there is a cranking sound, but the car does not start, it means you may have a broken ignition switch.

Your car key fails to turn:

When your car key is stuck to one position and does not rotate to the start position, it indicates some problem with the ignition switch.

Car Stalls:

If you see your car stalling once you start the engine or after you drive, it means there is some problem with the ignition switch. 

When no noise comes from the starter:

Generally, when you turn on the key to the starter position, it makes some sound. If your car does not sound, there can be a blocked electrical path. The problem may be due to a dead battery.

Dashboard Light Flicker:

If your car’s dashboard is flickering while driving, it also indicates some problems with the ignition switch. However, this is a rare indication of a bad ignition switch.

How To Wire a Starter Switch: What Causes Ignition Switch Problems?

Your car or vehicle’s ignition switch may fail for several reasons, including broken springs, temperature problems, or worn ignition switch contacts.

How To Wire a Starter Switch: Ignition Switch Replacement Cost

The cost of ignition switch replacement depends on the car’s model and labor cost. However, the average price comes to around $120 to $ 250. Here, the ignition switch cost is $20-$25, and the labor cost is about $100 or $200.

The replacement cost depends on whether you are replacing only the switch or the whole ignition barrel.

How To Wire a Starter Switch: Push button switch

Push button switch

How To Wire a Starter Switch: How can you wire your Ignition switch?

You can efficiently work on the ignition switch at work and need not spend too much on its repair and replacement. How can we do that? We will explain it in the following steps, but the focus here is on the key-based ignitions, not the push-button switch.

Step 1: Understand all the wiring of the ignition switch:

First of all, you have to understand the ignition switch wires. First, see your vehicle’s make and model, as all cars have unique ignition switch wiring diagrams. Look for all the locations and functions of the pin behind the ignition switch and see where it wires into the battery and the vehicle ignition system. 

Step 2: Disconnect the battery of the car:

You can start the replacement process when you know all the ignition switch wires. However, before you do that, disconnect the battery. It is a safety measure that avoids turning on the Ignition while working.

The car’s battery has two positive and negative terminals, and it is advisable to remove the negative terminal first. Also, keep it safe and avoid contact with the car or the terminals while working.

Step 3: Free away any trim pieces near and around the lock barrel:

This step is the fussiest part of ignition switch replacement as you have to disassemble the interior trim of the lock cylinder. The local cylinder lies on the steering column, dashboard, or center console, and you can easily take out the steering-mounted switch. 

First, remove all the plastic trims and the protective panels surrounding and covering the lock cylinder. You will also notice the plastic clips that surround the cylinder. Press them with a screwdriver and release all of them. 

You can access the ignition switch only after detaching the steering column in some cars. For this, you can take a steering wheel puller. However, be careful as you can trigger warning lights or airbags.

Step 4: Put the key inside and turn it towards the ACC position:

You cannot disassemble the ignition switch in some cars without the key, and you have to put the key into the lock barrel and turn it towards the ACC position. With this, you can pull out the ignition switch easily.

If you don’t have car keys, you can use a flat screwdriver for this task. Insert the flat head of the screwdriver into the slot and twist it as you do with the key. Be careful and apply a gentle force; otherwise, it can damage the barrel.

Thankfully, some cars have an easy and safe process to remove the ignition switch. There is a minor release pin around the ignition unit, take a flathead screwdriver, press down this release pin, and you can free up the ignition module.

Step 5: make the ignition switch free from the steering column:

Whether you are using car keys or a screwdriver, you can gently tug into the ignition switch module through the release pin. Now, carefully, pull out the whole ignition unit. If you face any issue while pulling, you are not pressing it hard enough.

Step 6: Double-check all the wires of the ignition switch:

You studied wires in the first step, and it is time you remember all these wires and find them here. First, look for the positive power lead wire that connects the ignition switch to the battery, and it is a red and thick wire with power always in ON mode.

Now, connect this wire to the BATT pin of the controller. Attach a matching terminal to this wire’s end when you find this wire. With this, you can firmly secure it to the back of the new ignition switch.

Step 7: Repeat the same step for all three other wires in the ignition switch.

Once you secure the BATT or battery wire to the back of the ignition switch, repeat step 6 for other cables. Take a multi-tool, fit the right terminal of each wire, and fix it to the corresponding pins. 

When you connect these wires, note their color:

  • Accessory or ACC – violet/purple wire
  • Starter or ST – Yellow wire with red stripes
  • Ignition or IGN – Yellow/red wire

However, you can’t rely on the colors, and thus, you need a wiring diagram for the particular car and its model. In some vehicles, you may get wires with different colors and stripes. 

As a thumb rule, here are some colors:

  • Red – Power, ignition, or other functions that require a lot of electricity
  • Brown/Yellow – Starter
  • Dark Green – Ground

Step 8: Fix the new ignition switch module:

Once you complete the wiring of the ignition switch connection, you can move on with the previous steps in the reverse direction. Use a flathead screwdriver and apply pressure to the release pin. You can smoothly push the newly wired ignition switch in the slot.

While pushing, line up all the grooves and keep going until you hear a click sound from the release pin. Once done, it’s time for you to test this new ignition switch.

Step 9: Test the new ignition switch:

Once the ignition switch is wired correctly and fixed in one place, connect the car’s battery (12 volts). Attach the negative terminal and positive battery terminal. Now, insert the car key into the lock cylinder and turn on the Ignition. Try to give a crank and start your car.

The engine must start instantly; if it doesn’t, repeat the previous steps and see if you have made the correct wire connections. You will also have to repeat the steps if the symptoms of a faulty ignition switch reappear.

Step 10: Reassemble the interior trim of the lock cylinder:

If the new ignition switch works well, turn off the engine and start putting the interiors back. Also, disconnect the car’s battery. Screw, bolt, or clip everything back into its place. If you have detached the steering wheel, put it back onto the column. 

So, with this technical procedure, you complete the replacement of the faulty ignition switch. However, if you want to try an alternate option, you can go for hotwiring the car. Make a direct connection between the starter and the engine for cranking the engine. In this, you will bypass the ignition switch altogether. 


We understand that all vehicles are not the same; thus, we have a stock of custom-designed wiring for particular car models and make. Do you need an ignition switch wiring harness? Cloom has all the right and high-quality products for repair and replacement.