The Unmistakable Click

A Look at the History of the Turn Signal Sound

We all know the sound - click, click, click - of the turn signal, which is present in just about every car or truck on the road today. But have you ever wondered about the history of the turn signal and why it makes that distinctive clicking sound?

The turn signal first appeared on automobiles in 1909, but the click wasn't added until the 1930s. Inventor Joseph Bell patented a small electronic device that directed electricity to the outer turn signals. The device clicked.

Buick was the first automaker to add this new technology to its cars in 1939. For the first time in history, cars had turn signals that flashed, which also added a new layer of safety. Other automakers were slow to adopt this technology, and it wasn't until the 1950s that it really caught on and the clicking turn signals became standard on practically every new car sold.

So, what causes that distinct clicking sound? In many cars, the sound and flashing signals are generated by a thermal-style flasher. An electric current flows through the device, which houses a bimetallic spring, located within the dash.

When you turn the signal on, a current is sent through the bimetallic spring, located in the dash.

When you turn the signal on, a current is sent through the bimetallic spring that heats it up. The two metals within the spring heat up at different rates, forcing them to bend in a certain way. The bending does two things: It completes the circuit, sending current to the outer light and turning it on for a split second, and it makes that district clicking sound as the metal pops into position.

In newer vehicles, particularly those produced in the early 1990s and onward, you are likely to find an electronic relay-style system. This system is controlled by a microchip and an electromagnet. The chip regulates the electric current that runs through the magnet. Similar to the older style of flasher, this electronic relay completes the circuit to signal the outer light bulbs to turn on for a split second and then repeat. When the circuit is complete, it makes that familiar clicking sound thanks to an added bimetallic spring - through the spring technically isn't needed. It's just a helpful sound to indicate to the driver that the turn signal is active.

Much newer vehicles rely on a turn signal system that is completely chip controlled. There are no moving parts, which means no bimetallic spring, yet they still make that clicking sound. How? It's all electronic! It's a "fake" sound. It's just there because we expect it to be and lets us know our signal is on.