How to Wire 3 Wire Trailer Tail Lights
Question:
Accidentally, forgot to unplug lites. Trailer has red,blk,and white wires. Dont know what order the red,blk and white wires go back on six colored wiring harness. red on red and blk on blk didnt work. theres blk,brn,blue,red,green,and white. tried white on white blk onblk and red on red alredy, puzzled
asked by: john g
Expert Reply:
To determine the correct wiring for your trailer you will need to use a circuit tester, item # PTW2993, and attach the wires from the connector by function only. The light wires should be as follows, red is the stop turn wire and the black is the running light wire, the white wire is the ground wire and should be connected to a suitable ground on the trailer frame. The easiest way to get it right is to connect the taillight wire, usually brown from the 6-Way connector (see link) to the black wire on the light temporarily and look at the brightness of the light. Then connect the brown wire to the red wire and check the brightness of the light. The brighter connection should be connected to the green (right) or yellow (left) stop/turn circuit, and the dimmer light wire should be connected to the brown running light circuit.
The black wire from the trailer connector is usually 12-volt power and the blue wire is for trailer brakes. The white wire from the trailer should be grounded to a suitable ground on the trailer frame.

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