[ZR1North]

Originally Posted by -=Jeff=-

This is from an 88, probably the same in later years but maybe not

GM used the filaments of the bulbs to their advantage, if I apply 12v to both sides of the bulb it will be off, but with LEDs that does not work, since the Bulb is basically a short, the new LEDs are not.

IF I were to place the LED in the front of my car and remove the front Side marker it will work in both cases

I have a 2 relay (per side) solution which might be the best I am going to get. it will change the wiring of the marker light and a ground will need to be added, But it would work.

Also in current OEM state, if you put LEDs in the front side marker, they will only with parking lights OR Turn signals, not both ( due to GM Design)

I took a look at my 91 wiring this evening, and I see what you mean about the dual-side use of 12V. It's another example of how GM used bulb filaments for circuit control, a little like what they did with the fog light disable when switching from low to hi beam. I see how a couple of relays could solve the switch to LEDs for the front signals and side markers. I'll have to sleep on it - just did a relay mod to address the issue I had with fitting the HID fog lamps and need to tackle some other (non Zee) things on my to-do list before getting the wire strippers out again.