Rated 4.9 Stars based on 6,700 reviews
Fast Delivery
Customized Service
HomeHowHow Do Turn Signals Work: Let Us Find Out

How Do Turn Signals Work: Let Us Find Out

How Do Turn Signals Work? Owning a car is a thrill most people can attest to.

However, knowing how to operate one is another hurdle to overcome.

For instance, vehicles have turn signals that improve safety and rarely malfunction, save for faulty bulb filaments.

But, in addition to the function, how do turn signals work?

Briefly, a turn signal has a simplified circuitry consisting of a flasher, turn-signal switch, dual filament bulbs, indicator bulbs, emergency bulbs, and an electrical ground.

Each turn signal part plays a key role in an effective working turn signal, as we’ll see in today’s article.

Let’s get to it.

Automobile Turn Signal Flashers

Automobile turn signal flashers are essential vehicle equipment that helps drivers alert road users of their intended actions. 

While there are a variety of blinkers, currently, modern vehicles use solid-state flashers and earlier designs like thermal flashers.

How do turn signals work?

When you press the ignition key, you provide power to the turn-signal circuit. 

Then, the power proceeds to the thermal flashers via a fuse panel before terminating in the stalk situated in the steering column.

You’ll activate the circuit when you lift or press the turn signal lever.

The activation will direct the electrical power to the left or right side lights to begin flashing.

A signal lamp

(A signal lamp)

Power feed and flasher unit

Generally, a standard flasher unit powers the turn-signal system.

The flasher accumulates electricity solely if the fuse buss remains ‘Hot in Run’ through a fused, switched link.

 Then, a wire further connects the flasher to the steering column’s turn signal switch’s center wipe.

Car turn signal control system lever switch

(Car turn signal control system lever switch)

Also, note that heat inside a tungsten bi-metallic ‘strip’ disintegrates or creates the flasher contact in the power output position.

 When operating, the strip bends due to the different expansion rates of the two unique metals. 

Moreover, when you load the flasher unit with system lamps, the strip will break the contact switch by heating up, then bending upward.

Later, it’ll swiftly cool down, create another contact, and the load will heat the strip again, thus opening it.

The process results in a flash.

The turn signal switch

The steering column has a toggle stalk that moves a turn signal switch contact to a perfect spot to indicate a turn.

For its electric function, the flashers send current to the switch via a wire, which reaches its center contact. 

On receiving the current, the switch’s center contact dispenses it to the left or right signals depending on the switch movement. 

For example, if you choose a right turn, you’ll press down the stalk, and the center contact will rotate upwards to touch the wires connecting to the dash, rear, and right front indicator bulbs.

Indicator bulbs

  (Indicator bulbs)

The circuit is normally complete due to the bulbs being in grounded fixtures.

As that occurs, the filaments will light up until they turn off due to a circuit contact break.

Suppose you see the lights turning off and on. It’ll indicate a constant opening and closing of the flasher’s contact.

Troubleshooting the Turn Signal system

  • Failure of a single lamp is the major problem a car lamp system will have in its lifetime.
  • Inspecting the bulb and then the power to ensure they’re good is advisable.

Checking for power at your socket:

  • First, obtain your DVOM and adjust it to the volts scaling ≥ V X 50. Then, put on the key and switch on the signal troubling you.
  • Cautiously put one end of the meter’s probe to good ground and the other into the socket.
  • If the reading is as follows, 0-to-12-to-0, power goes to the system, and lamps function properly. The only issue is in bonding.
  • Therefore, switch off the system’s power, then return to the malfunctioning socket.

Dead system

  • Examine the bulb and ensure it’s effective.
  • Next, check and clean the bulb socket. Also, apply some dielectric grease to avoid issues in the future.
  • Look into your fuses.
  • If the flasher relay or module has a problem, the purpose is to buy a new one and make the replacement.
  • Lastly, check the turn signal lever switch.

Rear signals are working, but front signals aren’t (or the opposite)

Begin by separating the pair of wires on the damaged ends from your column plug. Then, use your voltmeter to find the wire’s measurement. If the reading is 12 volts, the ground wire could be open.

The next step is installing or replacing the ground from every socket to the sturdily framed ground.

Right- or Left-side turn signals are not working

Here, you will apply the same method for the rear and front end, only focusing on the damaged part.

Flashing in every rear turn signals

Look for a short circuit amid the signal and brake lamp circuit in the turn signal switch.

Furthermore, inspect for shorts in the harness and column plug. Then, when the power is off, take the harness out but select either side.

The should be a continuity in the brake lamp’s off position and no reading displayed for the side selected on the brake lamp circuit.

However, if you get different results, re-check the harness and switch and replace/repair accordingly.

car brake lights

(car brake lights)

How to use your turn signal

Using a turn signal is an easy process.

  1. Most cars have gray or black turn signals as a long lever on the steering column’s left side. If you move it upwards or downwards, the lever will enable the light on the car’s right or left side to flash.
Turn signal lever

(Turn signal lever)

  1. If you want the turn signal indicator to indicate a right turn, ensure you are within approximately 30 yards of the intended turning corner. Then, use your left hand to move the lever up while in the right-turn lane.

After the turn signals clock in, you will see a flashing arrow on the instrument cluster that points to the right.

A clicking tick-tock sound usually accompanies the flashing light indicating a proper functioning turn signal.

Get back to the steering wheel and proceed with your driving.

  1. Turning your car to the left is similar to procedure (b) above but with minor differences. Keep your car at 30 yards from the intended rounding corner. While on the left-turn lane, gently push the signal lever down using your left hand.

The events following will be like those in the right turn signal.

Note: Ensure your right hand is at the steering wheel when using the left one.  Moreover, it is advisable to switch on the signal in advance to alert other drivers of your reason for slowing.

  1. Under normal circumstances, your turn signal will automatically go off if you turn at 90 plus degrees angle. However, less than 90 degrees will require you to do it manually.

What Is a Thermal Flasher?

A thermal flasher is a small round electrical cylinder situated in a fuse box of an automobile. It’s cost-effective, and manufacturers construct in the steps below for its use:

  • First, it has an electrical contact that enables electrical current flow into the thermal flasher.
  • Also, the contact connects with a curved piece of spring steel.
  • For the second piece of spring steel, they will wrap a resistive around it.

Principle of Working

Usually, the working process inside a thermal flasher is instantaneous.

It starts with the hazard lights switch or turn-signal bar activating the thermal flasher, resulting in a chain of events.

  • If you raise or push down the car’s turn-signal bar, the circuit becomes complete. Then, the current will move into the bulbs in the turn-signals lights via the flasher. At first, the minimal current flow doesn’t establish contact with the spring steel and only flows to the signal bulbs through the resistive wire. Here, a bulb cannot make a dim glow.
Turn signal button

(Turn signal button)

  • Next, the spring steel will heat up and enlarge due to the current’s resistance. The expansion provides contact and enables current flow that switches on the turn-signal bulb.
  • If the spring steel cools off later on, there will be a disruption in the electric current flow. Consequently, the turn-signal bulb will go off.
  • Swift cooling and heating in the flasher lead to the turn-signal bulb flashing once or twice each second. When the spring steel touches the contact while expanding, it produces a sound you often hear on the turn signal.

What Is a Solid-State Flasher?

A solid-state flasher is the latest electronic component in late-model cars. It encompasses a digital technology that requires computer chips for its activation.

Therefore, on activating hazard lights or turn signal switch, the current generated from the flasher will go through the timing chip.

As the timing chip experiences the current flow, it’ll use a transistor to activate, disrupt, and restart the current flowing to a turn-signal bulb.

You can liken this process to when a thermal flasher generates a blink.

Additionally, solid-state flashers mimic thermal flashers in producing a clicking sound for a more audible signal.

(car headlights)


In conclusion, turn-signal indicators provide safety to road users by ensuring drivers communicate their intentions to pedestrians and other drivers.

Some turn signals you will likely find in the market include a solid-state and thermal flasher.

Despite applying different principles, their core function is acting as turn signals.

Hi I am Christa, sales manager of Cloom.

I have extensive expertise and experience in wiring harnesses and I believe I can help you.

And we have a very professional technical team who can clearly understand the customer’s needs and give professional suggestions and solutions after receiving the drawings.

If you also have wiring harness needs, please send me the drawing so that we can give you our quote and start our business.

Background media

For Better Future
and Business
Let’s Talk Now!

Fill in your details and we’ll get back to you in 24 Hours.

Contact Form Demo


[email protected]




3rd Floor, Nanhai Plaza, NO.505 Xinhua Road Xinhua District,
Shijiazhuang, Hebei, China. 050057


© 2007- 2023 Cloom tech. ALL RIGHTS RESERVED.



Subscribe to our newsletter for the latest updates, exclusive offers, and exciting news delivered straight to your inbox.