The Wiring - How Turn Signals Work | HowStuffWorks How Turn Signals Work. by Karim Nice. The Wiring. Prev NEXT . Let's take a look at how the turn-signal circuit is hooked up. The turn-signal circuit gets power when the ignition key is on. The power goes through a fuse panel into the thermal flasher. From there it goes to the stalk on the steering column.Author: Karim Nice Practical LED Indicator And Flasher Circuits | Nuts A two-LED flasher is a simple modification of this circuit, but is arranged so that one LED switches on when the other switches off, or vice versa. Figure 14 shows the practical circuit of a transistor two-LED flasher, which can be converted to single-LED operation by simply replacing the unwanted LED with a short circuit.