Hey all. in the f3 ABA. the wire colors in the dummy a unit. You have yellow, white, black and a red. see picture.. wondering what colors are pos. Net. For lights. 
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Most lighting in MTH engines have a common "hot" line called a PV line. Lights or LEDS are activated when a ground is applied through the PS2 or PS3 board.
As Jon stated, if this is PS-2 a common PV for lights and coupler. So from you picture looks like White is the common Positive Voltage to all lights and the coupler. The negative control is the other wire. Not sure the color code is standard in trail A model to model/year to year, so best to trace.
I this case it looks pretty simple. G
Yeah its ps2 3volt. rear number boards stay lit. The cab and headlight are on reverse lights. the cab and marker have the white and red. I'm guessing that red is the trip.. to turn on the lights from remote.
Thanks Jon and George!
