turn signals

automotive types out there…
what causes that clicking noise we hear when the turn signal is selected? I believe it’s there as an aural advisory that they signal has been selected, but what actually makes the sound?

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“You screw up just this much, and you’ll be flying a cargo plane full of rubber dig shit outta Hong Kong!”

In my car, at least, the clicking noise is caused by the sound of a relay (electronic component) actually switching back and forth to open and close the flow of current to the blinkers. I know this 'cause one time I had to fiddle with it once long ago when something was messed up, and you could hear it click in sync with the turn signal.

But then, I drive a 1973 Dodge Dart…I’d think that the technology for cars in the last 25 years would’ve advanced beyond having big old solid-state components under the dashboard. Anyone?

The noise is made by the turn signal relay. The clicking made by the relay and earlier flasher mechanisms wasn’t originally intended as an alert - it was just the noise it made. But people are now used to audible feedback when the turn signal is on, and it is sometimes enhanced on purpose.

Before the widespread use of cheap electronics, the mechanism most frequently used to flash the turn signals automatically was a simple bi-metal strip.

A bi-metal strip is (surprise!) a strip of metal made of two kinds of metal pressed together. When they heat up, the two different kinds of metal expand at different rates, so one gets a little bit longer than the other. But since they’re stuck together back to back, the strip bends in the direction of the shorter one.

So to make the turn signals flash, you run the electricity for the turn signal bulb through a bi-metal strip that is bent slightly, so that the free end is touching the contact that the turn signal bulb is connected to.

When you turn on the electricity using the main turn signal switch, the electricity runs through the bi-metal strip to the turn signal bulb, making the bulb light up. But the bi-metal strip also begins to heat up.

When the bi-metal strip heats up enough (they are designed to have this happen in a second or less, usually) the bending action caused by the heat overcomes the bend the strip was formed with, and the free end of the bi-metal strip snaps away from the contact the turn signal bulb is connected to. This stops the electricity from going to the bulb (which then goes out, obviously) and makes an audible clicking sound.

Now that the electricity is no longer flowing, the bi-metal strip starts to cool down. After a second, it is cool enough for the bend it was formed with to once again prevail, and it snaps back to its original position. This makes another clicking sound, allows the electricity to flow through the turn signal bulb (making it light up again), and the cycle starts all over again.

This continues for as long as the main turn signal switch is on.

This was a simple, reliable (and cheap) way to get a bulb to flash with the technology available at the time, and the clicking sound was just a happy by-product.

With today’s cheap technology, it wouldn’t surprise me that flashers are now all electronic, and the click is added deliberately.

Ugly

My question is why is the click not 20 dB louder so the idiots who drive without realizing their turn signal has been on for the last 30 miles would wake up.

Wouldn’t work - they’d just have the stereo up far enough to drown it out. Maybe cut off the audio system while the blinker is on, or make the indicator bulbs on the dash about 3 inches in diameter.

Actually, I wonder why they can’t just put a timer on the damn thing that will turn it off after a couple minutes. Shouldn’t be any more complicated than the self-cancelling mechanism that realizes you’ve turned.

What I’d like to see, personally, is a loud, annoying alarm that sounds whenever you make a significant turn without using the signal. You’d still be able to swerve in an emergency, but it might train some folks to actually signal their turns. Make it kill the stereo and anything plugged into the lighter, too, while it’s at it.

No, I think what we need is a device that will not even allow the car to turn if the turn signal was not used. (not sure how it work for swerving, though :frowning: )
It would be great for those idiots that wait till the light turns green, and THEN put on their left turn signal.

I’m pretty sure Cadilac has this.