I'm trying to make my fog lights work with the parking lights, so I have one continuous strip of light. While I'm handy enough to craft it, designing the circuit so that I retain proper factory functionality is beyond my skills. I'll try my best to explain what I need, please go easy on me if I mess up some terms.
- The rear parking lights consist of one 21/5W (leftmost, also brake light) and one 5W bulb (center). The fog light uses а 21W bulb (rightmost, in the trunk partition of the taillight).
- Since the fog light is driver-side only, I'll add another 21W bulb to the passenger side.
- I'll run a wire from the driver-side 5W parking light, into the trunk, through the components that you kindly suggest I use, and finally to both fog light bulbs.
- There needs to be a resistor somewhere along the line, and the bulbs need to be wired in paralell, due to the bulb holder design.
The result of this mess - when I switch the parking lights on, the fog lights also light up - using 5W of power each (hence the resistor), so they are exactly as bright as the other two bulbs.
Here come the tricky parts:
- I have no clue how to calculate the proper resistor needed to power two 21W bulbs, wired in parallel, at 5W
- Maintaining the fog light functionality - the driver side bulb should be able to draw full power from the factory wire when needed
- I would like current to only go one way - no current should go from the fog light to the parking light, or from the parking light to the headlight switch module
- The original fog light circuit needs to be the default - the CANBUS system checks the bulb at startup and I refuse to live with a "bulb out" warning
I would like to use simple components - relays, diodes and so on.
A million thanks!