Why Do Turn Signals Make That Clicking Sound?

Your car can make different sounds for different reasons. However, not all of them signal a problem. Some are completely harmless and are simply there to inform you. One such sound you're probably familiar with is the clicking noise that occurs when you use the turn signals. But why do cars make that sound? The answer lies in how the turn signal mechanisms worked back in the day.

In older cars, when the driver activated the turn signal, an electric current would heat a bimetallic spring or metal strip inside a cylindrical flasher unit. The rise in temperature would then cause the spring or strip to make contact with another metal tab, completing the circuit and lighting the turn signal. As the thin metal inside the flasher quickly cooled down, the two points would lose contact, breaking the circuit and turning the light off. 

This cycle of heating and cooling would continue until the driver turned off the signal. This entire process of making and breaking the contact between the bimetallic spring and the metal strip produced the familiar rhythmic clicking sound, and the metal casing of the flasher unit amplified it.

Turn signals predate the most beautiful pre-war cars ever made but they weren't widely adopted until the early 1950s. Interestingly, the clicking sound that turn signals make wasn't intentional, but rather a mechanical byproduct of the mechanism used to flash the light. 

On most modern cars, things work a bit differently. Manufacturers now use digital commands to flash the turn signal lights, so there's no actual mechanism to produce the clicking sound. However, since most drivers are used to the audible cue, automakers simulate it through the car's speakers. The clicking sound serves as a helpful reminder that your blinker is active. After all, accidentally leaving your turn signal on can easily confuse other drivers on the road. 

That said, make sure you don't confuse this simulated clicking with a different type of clicking sound you might hear when turning the car. That could indicate a potentially dangerous problem with the constant velocity (CV) joints.