Quick & dirty wiring job cause I'm going out of town next week and don't want to pull a trailer just to have turn signals.....
LED running lights work just fine... ... ... that was the easy part. Turn signals require resistors wired in parallel. Brake lights also require resistors. Only had two resistors, so had to put in conventional light fixtures to get brake lights..... ordered two more resistors.
The wiring loom is split to route wires to the left and right sides. The crew who took the box off didn't label any of the connectors, so without digging into a wiring diagram, I'm not positive about what they hooked up to, one should be the DOT middle light and the other should be the license plate light. Doesn't make any difference... . my lamp out warning light is off and lights function as they should.
I found running lights, turn signals, and brake lights on both the right and left sides... ... . used 'em all. I tapped my marker lights which included license plate lights into the right side running lights. If memory serves me correctly, I ended up with two black wires on the left side and three on the right that are not used. Don't know what they're for without digging into the wiring diagram. Still need to install backup lights, so I believe at least two of the 'extra' wires are accounted for.
Still need to deal with the 4 wire to 3 wire LED thing. MCrossley's suggestion about getting the dealer to reconfigure the wiring may be the way to go, but I'm more apt to try a converter. If a converter will work for a trailer, it should work for a flatbed. The nice thing about the truck wiring is that the trailer wiring is independent so you don't have to tap into anything, it's already there and set up.
Once I get back from my trip, I'll get the wiring sanitized and I'll be done.
RL-650 Load Resistor kit
6 Ohm, 50 Watt load resistor kit
Solves most LED turn signal problems
Connect one across each LED turn signal bulb to simulate filament bulbs
$ 4. 95 (From superbrightleds)
http://www.superbrightleds.com/cgi-bin/store/commerce.cgi?product=CAR
I bought 6" oval 56 LEDs from superbrightleds. They are bright!!!!!!! If you can get all the light functions working in one light, one light on each side is more than adequate. I'm gonna have 2 ovals in the tailboard and 1 in the headache rack on each side... ..... I probably won't need backup lights.
Have resistors:
http://www.ledtronics.com/datasheets/auto_index/auto_index.htm
Have wiring converters:
http://www.wiringproducts.com/?target=dept_35.html
Just crossed my mind that it might be plausible to use the trailer wiring system for the lights on the flatbed, but you'd then have to deal with the lamp out sensor... ... ... ... ... . this stuff is getting way too complicated.