What Does Some Trailer Wiring Have 2 Brown Tail Light Wires

Updated 04/05/2018 | Published 04/04/2018

Products Featured in This Question

Hopkins Wiring Harness with 4-Pole Flat Trailer Connector - Trailer End - 4' Long

(78)

$6.58

Mighty Cord 4-Way Flat Trailer Connector - Wishbone Style - Trailer End - 25' Long

(43)

$24.89

4-Way Wishbone Trailer Wiring Harness with 42" Ground Wire - 40' Long

(34)

$37.72

40 Ft 5-Way Trailer Wiring Harness - Wishbone Style - 30" Ground - 5' Auxiliary Wire

(176)

$34.36

Question:

there is a 5th wire coming from the trailer that is brown and yellow

asked by: Don

Expert Reply:

Common 4-pole trailer wiring like # HM38138 uses one wire, the brown one, for the running lights on both sides of the trailer.

Sometimes what is called a 'wishbone' harness is installed on the trailer and this simply uses two separate running light wires - brown with yellow for left and brown with green for right - to make it easier to connect to the trailer lights since that way no jumper wire will be needed to cross from one side to the other.

Some examples of wishbone style 4-pole trailer wiring are parts # A40W42B, # A10-4225VP and # A40W5B. The linked photo shows you a 5-pole set-up that also has the same dual-brown-wires for the tail lights.

The linked article that covers all popular types of trailer wiring will help clarify how the functions are assigned to each wire on a connector.