2009 honda Civic brake lights.Measured 3.7Volts at the light. I made a diagram with relays previously and I've just gotten around to updating this with a single Transistor instead of four relays (using TIP31 NPN). This is a greatly compacted circuit diagram and works real well. Electricity likes the path of least resistance, so when the brake is pressed the low resistance Transistor is chosen instead of the 80 Ohm bypass resistor.
