Camper Has Separate Brake and Turn Signal Lights But Truck Has Combined System 4-Way Flat

Updated 10/25/2013 | Published 10/24/2013

Products Featured in This Question

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

(847)

$23.05

2-to-3 Tail Light Converter for Towed Vehicles w/ Incandescent Tail Lights

(172)

$38.14

Question:

I have a ui vacioner camper and am tryin to get all the light going. The turn/brake has 3 bulbs and 2 wire coming out of each. My trailer and truck is the flat 4 wire set up. How do I wire this? Plus none of the marker lights work? I got a few on but they stoppd woking.....help.

asked by: Elaine

Expert Reply:

Typical trailers have what is called a combined system. This means that the brake lights and turn signals on each side are on the same circuit and the running lights are on their own circuit. Your set up sounds like a separate system where the brakes have their own circuit, turn signals have their own circuits and the tail lights have their own circuit.

Your truck has a 4-Way flat which means that it is set up for a combined system.

There are 2 ways to handle this problem: 1) You can change the wiring on the trailer to work as a combined system or 2) you can adapt the 4-Way wiring to work with the separate system on the camper.

I recommend converting the trailer over to match the truck because the combined systems are more common. You will need a trailer side 4-Way flat wiring harness, # A35W42B, and tail lights of your choosing to replace the existing tail lights. On the wiring harness there is a ground (the one covered pin) then the next pin has 2 wires coming from it. These are the running light wires for each side. Next to that is the left turn signal/brake lights, and the last pin is for right turn and brake lights.

The other method would require the use of a converter, # 118158. You would still need to install a 4-Way flat on the trailer side. The wires going into the converter from the 4-Way will match color for color. The brown running light wire bypasses this converter. On the output side then you would have a yellow left turn only wire, a green right turn only wire, and a red brake light only wire. This converter is not rated for very much power draw and may not be the best option.

expert reply by: Michael H