Turn Signal

Turn signal tech

Turn signals were developed a long time ago to solve a serious problem: to indicate what direction motor cars are going to go.  Previous to having illuminating signals, drivers would use their hands or even their voices to let others know which way they were headed. As soon as electric lights became practical, though, they became the technology of choice for both turn signals and front illumination.

Today illuminating turn signals are required by federal law and they are more relevant than ever. “Using your flashers” is one of the most important actions you can take as a driver. Yet, it’s amazing that some people don’t use then consistently. Too bad, failing to signal is the root cause of thousands of accidents per year. Despite their mission critical function, the technology behind them is relatively simple. We wanted a few more details and thanks to our friends at Beck Chrysler of Palatka, a local Chrysler, Dodge, Ram, Jeep dealer in Palatka, FL, we have the whole scoop. Let’s take a look.

Starts at the battery

A turn-signal circuit gets power from the car battery whenever the ignition key is on. The power goes through a fuse panel to a thermal flasher and then to the turn signal lever. Depending on the position of the turn-signal lever, the power either stops in the switch (no turn indicated) or gets sent to the left or right turn-signal lights. When the turn signal stalk is switched to the left or right, the circuit is completed through the filament of the light bulb and then goes to ground. The result is the turn signal illuminating.

The signal flasher

Signal flashers are what make turn signals blink. They are small, cylindrical devices, often located in the fuse panel under the hood. Here’s how they work: When power flows through the signal flasher, it goes through a special strip of steel that bends as it heats up. When it moves up, the circuit is broken and the strip cools down which reestablishes the circuit. This cycle repeats every second or so and this is what makes a turn signal blink.

Self-canceling signals

Most cars have a mechanism that shuts off the turn signal when you are finished making a turn.  The first turn signals didn’t have this feature and drivers often left their signals on for long periods of time. During the 1940s, various manufacturers started to equip their cars with self-canceling turn signals. This is the way it works: when you turn and put on your turn signal, the turn signal starts to blink. When you steer back to straight, the turn signal magically cancels itself.

Here’s how the magic works: On the steering column, there is a hub with four notches equally spaced. When you lift the turn-signal stalk to signal a left hand turn, a spring-loaded roller slips into a notch in the switch housing. At the same time, a plastic lever thrusts out into the path of the hub. This forces the spring-loaded roller out of its notch in the switch housing, so the stalk springs back to its centered position.

Mirror-based turn signals

For decades turn signals were mounted on the front and rear of cars and trucks. In the last decade, many car makers have installed turn signals in their side mirrors too. This is a great spot for the turn signal because they are an additional indication of turning and the driver can see them without looking at the dash.

LED turn signals

For over 100 years turn signals, and all other car lighting, was accomplished with incandescent bulbs. Today the transition from incandescent to LED bulbs is in full swing. There are several advantages to this. First, LEDs can last 10-100 times as long as incandescent bulbs do. Plus, they turn on faster. Yes, LEDs light up about a fifth of a second quicker than incandescents do. That may not sound like much, but at 65 miles per hour, your car covers 19 feet in a fifth of a second. LEDs could give someone just a little more time to react when needed.