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Discussion Starter #1 (Edited)
I had to break out the multimeter to figure out which wires the resistors needed to use when installing LED front turn signal bulbs on my '16 ST2. Figured I would share this to save someone the trouble.

It's the same for driver and passenger sides, though the 12v wire is a different color. Same place in the connector though.

Remove the headlight assembly. Unplug the connector from it.

It should look like the photo. I have circled the pins that must have the resistor across them. Red is 12v, black is ground. Just look on the other side and find the wire that goes to each pin. You're gonna have to undo the harness jacket. Get as close to where it meets the rest of the wiring harness as you can to give yourself slack on the resistor leads enough to mount them somewhere. Connect one resistor lead to one wire and the other lead to the other wire. It doesn't matter which end of the resistor is 12v or ground, just has to complete a parallel circuit. You can use a squeezy tap, or for a better connection if you're so inclined, strip and solder. The easy squeeze connectors have worked fine on mine, though.

You'll need to fasten the resistor somehow to a metal piece of the engine bay. There's a couple of good spots on the frame directly beneath and behind where the light assembly ends up sitting. You'll be able to easily identify them. Make sure the resistor "body" isn't touching anything plastic or wire, they get hot and could melt and burn things. I used 3M VHB double stick tape. Getting the wires back inside the flex jacket is going to be a little tricky with the taps and extra wires from the resistors, so do the best you can and make sure no wires will be worn down by the edges of the jacket. It's only a $15 part but it'd be a pain to replace so be careful.

focus-3_5-hid-harness-turn-signal.jpg
 

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Just so you know you can also just put a relay in for led flashers or canbus supported bulbs..this is it.
 

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Just so you know you can also just put a relay in for led flashers or canbus supported bulbs..this is it.
Unfortunately it's not that simple. The relay is built into the BCM, you can't just swap in a new one like a lot of other cars. Canbus bulbs don't work either; at least, nobody seems to have found one that does, otherwise everyone would just buy those and resistors wouldn't be needed at all.

https://www.focusst.org/forum/focus-st-electronics/40751-flasher-module-st.html
 

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Which resistors did you use? And which Leds. I have early 2014 ST3 so I think the front turns are different than 2015+
 
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