Terry:
The resistor (also known as a ballast or ballast resistor- if you're a Chrysler driver, the name will sound familiar), when mounted in parallel, will always have current flowing through it, even when you are applying the brake. You are correct that electricity will follow the path of least resistance, but not when things are wired in parallel. In parallel, the circuit supplying power, in this case coming from the brake light switch, acts as a manifold would in a car, and supplies each parallel component with the same amount of voltage, in this case, 12V. This means that while the LEDs are happily consuming fractions of an amp due to their high resistance, the ballast is allowing oodles of amps through to ground.
One of the main reasons that I switched to the LEDs (other than never having to go back there and wrinkle my hand trying to change bulbs
) was to reduce overall amp draw. This resistor is totally the opposite of what I was going for, since the amp draw hasn't changed one iota except when the running lights are on (that conversion is easy). Here's the plan:
Since no one has found a way to turn off the bulb sensing feature in the ECM on the pre-Mkv, I plan to fool it another way. The ECM only sends a small signal voltage (about 5V I believe) to the rear brake lights when the brakes are not applied to see if the bulbs are present and accounted for. The wire that carries this signal is on the brake light side of the brake switch, and is seperate from the brake light power. When the brake is applied, this signal is interrupted by the 12V current from the brake light switch that is heading for the brake lights. What I am planning to do is send that 5V reference signal through a low-ohm resistor to ground, away from the brake light bulb circuit, so that the signal still goes through they way that it would if the brake lights were there. In between the resistor and ground, I would wire a semiconductor (this is the part that I haven't had time to look up yet) that would interrupt the ground signal when it received the current from the brake light switch, thus making the ECM think that the 12V is there. Since the semicondictors are high resistance (even more than the LEDs), very little current would be consumed while the brake lights were lit, and the end result would be the same- no GP light. The only piece of the puzzle that I need is the name of the semiconductor (MOSFET?) Instead of amplifying the signal like a transistor, it interrupts it. I used to know what these were called. Once I get that, and figure out how to use it (which should be pretty easy), I'll get it wired in the car and start a new thread.
I also plan on modifying my blinker so that it still blinks at the correct speed with the LEDs installed. Right now, I have TWO MORE ballasts installed, one for each side, to make them work. I'd like to get those out of there too.
Let me know if you come up with the correct component name... I'm DYING to do this.
BTW- My house is in Weare! My wife and I are in KS while I'm in school for the next few years, but I hope to get back there when I get out. If home is where the heart is, I never left NH!
-Rich