I did an LED retrofit on a customer's car a few months ago and it's been working great, he got tired of replacing bulbs and ballasts, his car kept having issues every 3 months or so even with different headlight housings. Contrary to what I was told, the LEDs are noticably brighter than the 6000k HID's in my DTS, I had both cars there so I was able to compare side-by-side. here's the writeup I did for a facebook group back when I did the install, it's surprisingly simple and totally removes the ballast from the system, it's only a block-off plate afterwards. High beams still work and no errors at all
facebook post said:"Use these exact LEDs, others will require you to keep using the ballast, which to me defeats the point of doing this conversion in the first place. installed this way, your ballast can be totally corroded or filled with water without affecting operation
Throw out the silver braided cable for the factory bulb & cut the other connector off going to the ballast, then connect the 2 black wires to each other. Next, connect the red wire from the LED's to the yellow ballast wire, and the black wire from the LED's to the other 2 black wires from the ballast connector. Route your wires and find a spot inside the headlight housing for the resistor and you're done! Just reinstall the lights.