How to Rewire an Old Cattle Trailer
Updated 10/21/2013 | Published 10/18/2013
Products Featured in This Question
Question:
I have an old cattle trailer that I am going to re-wire. It has apparently been re-wired several times and is a mess, so I am going to strip everything out and start over. I have purchased a 7 blade wiring harness. It has the wiring color coding on it and where each wire goes. The only two wires I am not sure of are the black and yellow wire. Black says to battery and the yellow says it goes to Auxiliary Power. I think this really meant for RVs but it will work. Their instructions: Green to Tail Marker lights Red to Left Turn and Brake White to ground Blue to Electric Brakes I have electric brakes that are not currently hooked up and plan to hook them up and Brown to Right turn and Brake. I plan to purchase new wire and re-run wiring on the harness system. I have a 2001 Dodge Ram 150 pick up.
asked by: Donald C
Expert Reply:
It sounds like you are on the right track to rewire your cattle trailer. You are correct about the wire colors on the 7-way connector that you purchased. The colors that you see on the 7-way connector are typical for RV style trailers rather than utility, cargo, or livestock style trailers.
The black wire should be connected to the terminal in the 7-way connector labeled black. This is the terminal in the 11 oclock position when you are looking at the back of the trailer connector (see photo). The black wire is to run 12v power from the vehicle to a 12v trailer battery or another accessory on the trailer that requires 12v power such as loading lights or interior lights.
If you stay with the RV style color code, the yellow wire will connect to the center pin on the 7-way trailer connector. This is typically used for reverse lights which are not commonly used on utility, cargo, or livestock style trailers. If your trailer has reverse lights, then you can run the yellow wire from the center pin on the trailer connector to the reverse lights on the trailer.
Often times, people will run the wires from a 7-way such as yours to a junction box like part # 38656. From there, they will run the standard wire colors to the trailer lights, brakes and battery. I have attached a photo that shows how this setup works in the junction box. Most molded 7-way pigtails will come wired with the RV style color code. If you ever need to replace your 7-way connector in the future, you could simply open the junction box, remove the connector and wire loom and install a new, molded 7-way trailer connector.
I have attached a video showing the installation of the junction box. In this video, our installer uses a 7-way molded connector with the RV style color code like your 7-way connector. He also uses the traditional wire colors going out of the junction box to the trailer lights and brakes. He uses the appropriate lengths of 16 gauge Bonded 4 Wire, # 16-4B-1, for the trailer lights and 10 gauge Jacketed 2 Wire, # 10-2-1, for the trailer brakes and ground.
Additional hardware that you may need is 3/16 Inch Ring Terminals, # 44-5310A, 1/4 Inch Ring Terminals, # DW05702-1, 12-10 Gauge Butt Connectors, # 05732-2, 16-14 Gauge Butt Connectors, # 05731-5, and electrical tape.
Another option that you have is to wire the 7-way connector using the traditional color code. I attached a diagram that shows how the 7-way connector can be wired to stay with the traditional color codes. I have also attached a wiring help article that has information on trailer wiring.
Product Page this Question was Asked From
Pollak 6-Pole, Round Pin, Trailer Wiring Connector - Trailer End
- Trailer Wiring
- Trailer Connectors
- Trailer End Connector
- 6 Round
- Plug Only
- Pollak
more information >
Featured Help Information
Miscellaneous Media
Continue Researching
- Search Results: reflectors
- Search Results: conspicuity tape
- Search Results: round trailer light
- Search Results: oval trailer light
- Search Results: 4pin to 7pin
- Search Results: truck plug
- Search Results: rv receptacle
- Video: Feature Breakdown: Ranch Hitch Universal 5th-Wheel-to-Gooseneck Coupler Adapter
- Shop: Slide Hammer for Ranch Hitch 5th-Wheel-to-Gooseneck Coupler Adapter
- Shop: etrailer Anti-Rattle Hitch Stabilizer for 2" Hitches - Vinyl Coated Steel
- Shop: JC10 Halogen Mini Light Bulb - 2 Pin Base - 10 Watt - Soft White
- Shop: Trailer Wiring
- Shop: Fifth Wheel Hitch
- Article: Trailer Lighting Requirements
- Shop: Replacement Diverter Valve for B&B RV Water Centers - 1/2" MPT Connections
- Shop: LED Trailer Clearance or Side Marker Light w/ Reflex Reflector- 3 Diodes - White Base - Amber Lens
- Shop: Hopkins 7-Way RV to 4-Way Flat Trailer Connector Adapter with LED Test Lights
- Shop: Curt Towing Starter Kit for 2" Hitches - 2" Ball - 3/4" Rise, 2" Drop - 7.5K
- Article: Towing a Trailer? Let's Talk About Brake Controllers
- Article: Trailer Wiring Diagrams
- Video: Review of etrailer Trailer Hubs and Drums - Pre Greased Idler Hub - AKIHUB-545-35-EZ-K
- Q&A: Installing Trailer Connector and Junction Box on 20ft Gooseneck Trailer
- Q&A: Parts Needed to Rewire Vintage Trailer
- Q&A: Do I Need To Ground the Trailer Junction Box If Running a Ground Wire For Each Light To This
- Q&A: Replacing Lights and Trailer Connector on Boat Trailer Over 80 Inches Wide
- Article: Wiring Trailer Lights with a 7-Way Plug (It's Easier Than You Think)
- Video: Review of TecNiq Trailer Lights - Tail Lights - TN57AR
- Video: Review of Dexstar Trailer Tires and Wheels - Wheel Only - AM20545
- Q&A: Replacement Hub and Drum Recommendation for Dexter 8-247
- Q&A: Should Trailer Brakes Go On Front Axle or Rear Axle of Tandem Axle Trailer
on Trailer Wiring
