How is the turn signal indicator lamp lit w/o having a ground?
2. What keeps current flowing from, say, the BLRT wire (left) through the indicator lamp, into the BLST wire and lighting the right turn signals? The diagram shows directions of flow. Are there diodes somewhere to prevent backflows? Perhaps “Keys to Schematics” would help. It is at: A1. What you need (for the LED) are two diodes (1N4148 for example) a resistor (to step down the 12 V.) and (of course) the LED. The two diodes are necessary since you want to connect left and right to the same LED but you don’t want the current to flow back and turn on the four lights at once. If you don’t need it, you can avoid to connect the buzzer (a 12 V. Piezo beeper). Just remember that diodes and LED have a polarity that you have to respect. The resistor value depends on the LED. I am leaving for a trip in a couple of hours, so I don’t have time to give you all the details. If anybody is interested, I can fill in the blanks. Here is an ASCII art schematic Left —-[1N4148]–+ +–+–[Resistor]—[LED
