How to Adapt a 4 Way Flat Into A 5 Way Flat

Updated 04/04/2022 | Published 04/01/2022

Products Featured in This Question

Curt Vehicle Wiring Harness with 5-Pole Flat Trailer Connector - 60" Wire Lead

(13)

$11.75

Dielectric Grease for Electrical Connectors, 2 oz.

(1472)

$10.96

Curt Echo Wireless Brake Controller - 7-Way Plug-in w/ Bluetooth App - Up to 2 Axles - Proportional

(1716)

$224.90

Manual Override Button for Curt Echo Brake Controller

(88)

$62.95

Universal Installation Kit for Trailer Brake Controller - 7-Way RV and 4-Way Flat - 10 Gauge Wires

(3343)

$104.83

Hopkins 7-Way RV Style Connector with Molded Cable - Trailer End - 8' Long - RV Standard

(916)

$46.90

Question:

I have a 3500 HD duelly with built in brake assist tow package. I recently got a second hand cargo trailer. It has a 4 pin flat wire connector. This trailer had brakes originally but we’re inoperable when I purchased it. I had the brakes replaced and the wiring harness was replaced. Problem is I now have 5 wires on a 4 wire pin connector. Can’t keep the running lights working. Throw the 20 amp fuse every time. All other lights work and the brakes seem to stay working but not running lights looks to me like the installer tied the brake wire to the brown wire of the 4 way. My deduction is I should have a 5 pin. The way it’s hooked up sounds to me like I’m trying to pull to much power from that small 20 amp fuse. Am I on the right track ? Should I change to a 5 pin Thanks Cuevas Handyman LLC

asked by: Christina C

Expert Reply:

When it comes to your 5 wires on your 4 wire pin and you're wanting to run your trailer brakes I recommend switching the 4 flat to The Universal Installation Kit for Trailer Brake Controller - 7-Way RV and 4-Way Flat - 10 Gauge Wires # ETBC7. This kit will make your 4 flat into a 7 round plug and a 4 flat plug so you have both options. This will also activate the brakes on the trailer side. The wire configuration is as follows:

Green: Right turn/brake light
Yellow: Left turn/brake light
Brown: Tail/running lights
White: Ground wire
Blue: Brake controller output
Black: Battery hot lead
Purple: Reverse lights

On the trailer side you would have to cut off the 5 flat and put on The Hopkins 7-Way RV Style Connector with Molded Cable - Trailer End - 8 foot Long - RV Standard # H20046. This will give you the 7 round plug that will attach into your ETBC7. Then you can find the proper brake controller you need. I recommend The Curt Echo Wireless Trailer Brake Controller - 1 to 2 Axles - Proportional # C51180 and The Manual Override Button for Curt Echo Brake Controller # C83HR.

I also recommend The Dielectric Grease for Electrical Connectors, 2 ounce # 11755, this will help prevent electrical failures caused by corrosion and moisture.

I attached a review video link below.