How To Replace 4-Way Flat On Trailer That Has 7 Wires To It

Updated 08/19/2019 | Published 08/16/2019

Products Featured in This Question

35 Ft 4-Way Trailer Wiring Harness - Wishbone Style - 42" Ground

(858)

$27.01

Question:

My boat trailer has a 4 prong flat connector with 7 wires that needs to be replaced but I can only find a 4 way flat with 5 wires .. how do I wire this up

asked by: Stan

Expert Reply:

When a 4 flat connector on a trailer has 7 wires it usually means it either has extra grounds or extra tail light wires. Most likely if the extra wires are white then it is ground, if they are brown then they are most likely tail light wires. The only way to know this for sure it to test the wires for function using a 12V battery and a jumper wire. Touch one end of the jumper wire to the positive post of the battery, the touch the other end of the wire to all of the different wires to see what circuit illuminates. Make sure you ground the wire that you know is a ground before testing.

If it turns out you have extra ground wires on the 4-flat then you can use a standard Wesbar 4-Pole Flat Connector w/ Jacketed Cable - Trailer End - 4' Long part # W787264 on the trailer and combine the grounds to the ground wire (white) on the connector. If it turns out the extra wires are tail light wires, the easiest way is to use 35 Ft 4-Way Trailer Wiring Harness - Wishbone Style - 42" Ground part # A35W42B and combined the running light wires to the 2 brown tail light wires on the wishbone.

expert reply by: Heather A