How to wire a 7 pin trailer plug with electric brakes?

Wiring a 7 pin trailer plug with electric brakes is a very simple task that anyone can do. All you need is some wire, the right connector, and the correct tools to crimp them together.

Things required :

– Wire (recommended is to use 10 or 12 gauge wire)

– Exterior grade electrician’s tape (3/4″ width should do the trick)

– 7 pin connector with matching circuit, which can be bought from retailers like Napa Auto Parts, O’Reilley’s Auto Part, Checker, or similar store. Make sure you get the one that matches your make of trailer. There are many different manufactures on the market and only some will work for certain vehicles. 

– Crimping tool to crimp pins into the connector.

– Wire crimping tool.

– Pair of side cutters to strip wire.

Procedure :

1) Cut your 10 or 12 gauge wire to the length you need, and remove all the outer insulation with side cutters. Keep the area where you will connect the wires to make sure there is enough exposed copper for a good connection. 

2) Strip off about 3/8″ of insulation from both ends of each wire with a pair of side cutters until you get clean cuts without any strands hanging out. Make sure not to nick any other strands nearby when cutting. NOTE: In some cases, it may be necessary that instead of using just one color wire (for example red), you need to use two (one for ground and one for power). If your wire is 12 gauge or smaller, you can use a single color (red) for both wires. If your wire is larger than 12 gauge, we recommend using 2 different colors (for example red and black) for both wires. 

3) Insert the correct pin into each side of the connector in the matching row as shown in the picture below :

Note! It does not matter if all pins are not used, only that there is enough exposed copper on either side of the connector so you can get a good electrical connection with the crimping tool. If your wiring bundle is way too large to fit the 7-pin plug into where it goes on the vehicle’s bumper or frame, it is recommended to use a larger connector like a 4 or 6-pin.

4) On the wire side of the connector, insert all wires through the crimp pins and carefully put them back in place (don’t let any wires slip out). Take a look at each pin and make sure that there are enough copper strands exposed for good electrical contact with the crimping tool. Make sure no strand is nicked by any of the metal parts when inserting pins into plastic housing or they will break off during crimping. If you have had to strip two separate color wires instead of just one, don’t forget to install matching pins on both colors!

5) Crimp each pin solidly around its circumference with crimping so it cannot be pulled out. Use the crimping tool and you can get a nice clean crimp without any visible metal burrs or strands poking out. Some connectors have “easy to remove” pins which require removal with a flat head screwdriver to be reused on another connector by pulling it out slightly before they come loose from the pin. If your pins need this type of removal, make sure you don’t re-insert them into your connectors until after all wires are inserted and pinned down (otherwise they may fall back through when removing insulation).

Note! The best connection is made when squeezing together the metal parts of the wire pin with pliers as close as possible to connector housing while still being able to insert and remove the pin easily.

6) After all 7 pins have been inserted into the connector, insert all of the wires again firmly so no wire strand can be seen outside below insulation. The most common mistake when wiring a 7-pin is to use too small of gauge wire which results in loose connections and heat buildup inside the vehicle’s bumper or frame because of resistance due to large current flow.

7) If you need to pull back insulation on any other wires to make room for your connector (and you normally should), do it now before putting your connector in place. Some vehicles may have rubber grommets where the 7 pin plug goes through. Slide this grommet out if present before inserting the connector and replace once finished, otherwise, you will not be able to get that area open again after installation!

8) Insert the connector into the matching 7-pin plug until it “clicks” and make sure that you have pushed down your wire pins enough so they cannot fall back outside through-hole when removing insulation.

9) Cutaway any remaining loose strands of wire which may poke out or break off during use, being careful not to cut yourself or any other wires.

10) Make sure your connection is weatherproof by using heat shrink tubing for extra insulation and protection, or use sealed connector housing (if you have the option).

11) Test your installation and make sure all lights turn on/off correctly before putting the bumper cover back onto the vehicle. If they do not work right, you may need to remove and re-crimp your pins or re-pin the connector.

12) Secure wiring harness with zip ties and wrap up any exposed metal wire ends with electrical tape for extra protection against metal chafing, short-circuiting in case of scraping along with side frame, etc.

13) If any terminals/pins looked damaged or discolored after crimping, check again by sliding out the metal pin to make sure it was pushed in all the way (sometimes they are hard to see inside the plastic connector and still be able to remove them easily. If you feel that there is too much resistance when trying to remove a pin, something may have gotten jammed up inside and will either need to be cleaned out so it can come free, or the metal pin itself will have to be cut out if you cannot pull it back through.

14) After all pins/connections are made and your installation is complete, test everything again by plugging in your trailer and testing inside the vehicle with a test light before driving on road. Make sure all lights are working and turn off the vehicle to stop trailer lights from running your battery down.

15) It’s a good idea to always disconnect your negative wire any time you leave the vehicle unattended for a long time so it cannot drain your battery accidentally. Sometimes otherwise perfectly fine metal terminals can get corroded inside where they can’t be seen easily.

16) Now that your wiring harness is complete and you have tested all lights, it’s time to put the bumper back on the vehicle and re-attach any brackets or panels that were removed before. You may also need to re-adjust parking/turning/side marker lights by twisting the base where the bulb goes into the socket if your vehicle’s wiring harness was not compatible with factory 6-pin.

17) Finally, put any plastic caps or missing covers back into place so it looks cleaner and more professional when finished.

18) You also will want to keep in mind that even if you did a perfect job with the installation of a 7 pin connector, that does not mean it’s safe to back up while connected or drive on road. Make sure you know the law in your area and how to operate your vehicle properly before actually backing up or driving anywhere with the trailer attached!

That’s about it – now that you have learned all about 7 pin plug wiring, you can give yourself a pat on the back for a job well done and enjoy being able to pull a trailer again!

What is the Color Code for 7-Way Trailer Wiring?

SAE Standard J

560 specifies the standard for 7-way trailer plugs and sockets. The color code for this standard is as follows:

Black – Ground

Brown – Left Turn Signal

Red – Stop/Tail/Brakes of Trailer or Motorcycle

Orange – Right Turn Signal

Green with Black Stripe – Electric Brakes (E-Brake)

White – Clearance, Side Marker, or License Plate Light

Green with Red Stripe – Reverse Light(Back-up)

RV Standard J

The standard for 7-way RV plugs and sockets is Standard J, as well as all wiring for RVs, must be in conduits. The color code for this standard is as follows:

Black – Ground

Brown – Left Turn Signal

Red – Stop/Tail/Brake of Trailer or Motorcycle

Orange – Right Turn Signal

Green with Black Stripe – Electric Brakes (E-Brake)

White – Clearance, Side Marker, or License Plate Light

Amber – Running Lights/Clearance Lights

Blue with White Stripe – Emergency Break-away System for Fifth Wheel and Travel Trailers Only

What Size Wire Gauge is Used for a 7-Way Wiring Harness?

The size of wire used in a 7-way wiring harness is highly variable due to the different amps and watts of electricity required by different trailers. A typical set-up for most small trailers should be around 12 or 14 gauge wire, with larger trailers requiring heavier gauges such as 10 or 8.