How turn signals work

Turn signals work by pushing a lever up or down, which causes the vehicles turn signals to flash. This is what most people know about the turn signals located on their vehicles,

but how do they really work?

The wiring is important when discussing turn signals. A turn-signal circuit, powered up when the ignition key is on, and the power travels from a fuse panel into the thermal flasher on to the steering column of the vehicle. From here, the power either stops in the switch or continues on to the left or right turn-signal lights as well as the indicator lights on the dashboard, depending on the position of the turn-signal lever. Grounding takes place as the power flows through the filament of lights.

The thermal flasher is a small, cylindrical device, often located in the fuse panel under the dashboard of the car on the driver’s side. This part costs approximately $3 and auto parts stores usually have them. The thermal flasher, made up of electrical contact, spring steel, and a resistive wire, will work for many years before replacement is required. The electrical contact conducts the electricity from the fuse to the wire.

A mildly curved steel spring with an electrical contact attached to it and a resistive wire wrapped around a smaller piece of steel spring are the last items in the thermal flasher. When pushing down the turn-signal lever, the thermal flasher connects to the turn-signal bulb through a turn-signal switch completing the circuit and allowing current to flow. The spring steel does not touch the contact at first, so the only thing drawing power is the resistor. Electrical current flows through the resistive wire heat the smaller piece of spring steel and continue on to the turn-signal lights.

After about a second, the smaller steel spring will heat up enough to expand and straighten out the larger piece of steel spring forcing the curved steel spring into the contact and allowing the current to flow to the signal lights. The flash occurs when almost no current passes through the resistor and the spring steel cools. The spring steel bends back from the contact and the circuit is broken. After this, the cycle begins again and completion is at a rate of one to two times per second.

Another mechanism cancels the signal when the turn is complete, this is a notched hub located on the steering shaft. The hub has four notches placed equally around it and canceling the signal occurs by pushing a plastic lever on the turn signal into the path of these notches.

To signal a right turn, the turn-signal lever is lifter and a spring loaded roller falls into a notch in the switch housing, holding the lever in place while a plastic lever thrusts out into the path of the hub. As the hub continues to rotate clockwise, the notches hit the plastic lever and it rocks to let each notch pass. The hub turns counterclockwise when the wheel turns back to the left and pushes the plastic lever in the other direction. This action forces the spring-loaded roller out of the notch in the switch housing and the lever springs back into center position.

Turn signals in the mirrors are found on many cars today and contain high-intensity light-emitting diodes arranged to form an arrow pointing left or right. The light-emitting diodes, positioned behind the mirror glass, allow the driver to see only a dimly lit arrow while other drivers see a very bright arrow.

Turn signals

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