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HomeTips & GuidesTurn Signal Toggle Switch: How Does It Work On The Auto Wiring Harness?

Turn Signal Toggle Switch: How Does It Work On The Auto Wiring Harness?

About Turn Signal Toggle Switch: Most people take the turn signal for granted, forgetting the significant safety advantage they offer. 

Turn signal circuits are a simplified form of electrical engineering. However, the wiring is often confusing for most people. 

Read the article below to better understand the turn signal toggle switch.

Table of Contents

What is a Turn Signal Toggle Switch?

Often referred to as a turn signal arm, blinker switch, or turn signal lever, the turn signal switch is a lever normally positioned on the steering column

The turn signal switch is a single pole dual throw (SPDT) toggle switch.

Pushing it upwards turns on the right turn signal, while pressing it downwards turns on the left turn signal. 

Further, pushing the lever towards you will adjust the headlamp settings.

For older model cars, power routes to the turn signal switch through a flasher unit. 

The flasher is responsible for closing and opening the circuit to the turn signal switch and flashing the turn signals when activated.

 Furthermore, the flasher is responsible for the clicking sound you hear once you activate the turn signals.

However, with newer model vehicles, a computer system called the body control module controls the turn signals. 

Once you press the turn signal, an electrical system is sent to the body control module, which activates the turn signal lights and operates flashing duties. 

The majority of modern cars have a method of emulating the clicking sound made by traditional flasher units. 

Also, it’s important to remember that the switch is responsible for more than the turn signal lights. It might also manage the switches and dials or various other car systems. 

Depending on the design of the turn signal switch and the model of your car, you might have access to fog lights, windshield wipers, headlights, or cruise control.

Hence, the turn signal switch is sometimes called the combination switch.

A combination switch

A combination switch

Universal Turn Signal Switch Wiring Diagram

It’s important to understand the basic wiring of a turn signal system. 

Wiring Turn Signals That Have Their Separate Rear Bulbs

When the ignition key is on, the turn-signal circuit gets power, which goes through a fuse panel into the thermal flasher.

 From there, the power goes to the turn-signal switch on the steering column. 

The power flows to the right or left turn-signal lights or stops at the switch, depending on where you push the lever. Last, power goes through the filament of the lights and then is grounded.

Wiring in Turn Signals That Share the Rear Bulbs with Tail Lights and Brake

Unless the stop lights and turn signal lights use separate bulbs, the stop lamp switch is part of the circuit. 

Therefore, your turn signal light can blink on either side while you’re still applying the brakes. 

However, a faulty turn signal switch can hinder the stop lights from working properly, especially if the high-mount stop light functions while the regular stop lights aren’t working.

It would be best if you made the turn signal wires and brake light wires connect to allow the turn signal wires to override the brake light signal.

An easier way to do this is simply getting a tail light wiring converter for trailers. 

The tail light converter will combine the turn signal wires and brake light wires.

Some might have the tail light wiring running through them (four wire-into-three wire) while others don’t (three wire-into-two wire).

 This doesn’t make a difference because it doesn’t affect the tail light wiring.

 All you need to worry about is the turn and brake signal wires.

Also, it is important to remember not to use LED bulbs as the converters aren’t designed to accommodate the extra voltage.

What About Hazard Lights?

For hazard lights, all you need is another flasher unit and a toggle switch. However, the toggle switch isn’t the same as the flasher unit. 

Unlike the flasher unit, which uses a single pole dual throw (SPDT) toggle switch, the toggle switch uses a dual pole single throw (DPST) toggle switch.

Turn signal lights

Turn signal lights

Symptoms of a Bad Turn Signal Switch

Below are some of the most common symptoms of a faulty turn signal switch.

Turn Signal Lamps Don’t Work at All

The switch could be faulty if your car’s turn signals don’t completely work. However, the problem could be a result of several other problems.

 Therefore, before blaming the turn signal switch, it’s best to troubleshoot to be sure.

For instance, the problem could be a faulty flasher unit, issues with the BCM, or a blown fuse. 

Also, faulty connections, bad grounds, or several other problems could cause your problem.

Only One Side of the Turn Signal Lights is Working

Once you press the turn switch, internal contacts close to provide a pathway for electricity to turn on the turn signal on either side of the car.

Therefore, a failed switch can prevent electricity from reaching the right-hand or left-hand turn signal lights.

Other Car Systems Don’t Function Properly or At All

Often, turn switches are in control of various other vehicle systems. 

Therefore, any issues with your lever could affect the switches, causing fog lights and other components to fail to respond to their respective control knobs.

Despite your turn signal system working perfectly, you might still have to replace the switch to keep other car systems in good condition.

Want to Change Your Turn Signal Switch Wiring Harness?

Although a faulty turn signal won’t stop your car from running, it contributes to the safety of other drivers and yours. 

Except for emergencies, driving your car is not advisable if the turn signal switch is faulty. It’s always best to fix the problem before returning to the road.

You can pick three options when looking to change your turn signal switch.

Factory Switch Wiring Harness

Most people have a car using a steering column with an inbuilt turn signal switch. 

Therefore, you only need to use the vehicle’s wiring harness diagram to determine where each wire goes.

Steering Column

Steering Column

Aftermarket Switch Wiring Harness

Some people have a car without the factory switch in the column. 

The simplest method to add turn signals without a factory switch is using an aftermarket unit. 

However, a couple of people don’t like the appearance of the aftermarket unit and prefer hiding. 

You can accomplish this by simply placing the unit by the shifter or under your seat.

Custom Switch Wiring Harness at Cloom

The custom wiring harness utilizes correctly sized pin connectors to connect to the factory wiring plug. 

Therefore eliminating the need for you to splice or cut the factory wires. Thus providing superior quality connections and ensuring a longer lifespan without any issues.

We can custom-make switch wiring harnesses ideal for operating door locks, linear actuators, control panels, headlights, horns, power windows, sunroofs, and tonneau covers. 

Furthermore, they are ideal for various 12 V marine, industrial, and automotive applications.


The condition of your turn signal switch is important for you and those around you. 

Therefore, ensuring your turn signal switch is in good condition is important. 

For any inquiries regarding custom switch wiring harnesses, check out Cloom Tech.

I am Lillian Yang, having been a sales manager for over 10 years.

I have received many positive reviews from customers. They have praised our excellent service, on-time delivery, and high-quality cable assemblies.

For your projects, please provide cable assembly files/images/smples, etc., so that I can send you a quotation within 24 hours.

Contact me now and let’s get started on building your wire harnesses!

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