The majority of trailers use 7-way harnesses. Due to its diversified functions, the wiring of the trailer may seem like the most complicated part of your vehicle’s trailering system.
But this is not necessarily the case if you have a comprehensive 7 Way Trailer Wiring Diagram with Brakes.
To ease the trouble for you, this article furnishes you with a Wiring Diagram with Brakes along with an all-encompassing guide. Keep reading as you master the wiring.
7 way trailer wiring diagram with brakes:
Here goes the diagram for the wiring of the 7-way pin with brakes. What we get here are the primary 7-way plug and three additional pins.
The trailer’s 7-way plug supplies power for its brake lights, headlights, turn signals, taillights, and ground.
Just as a precaution, apart from paying attention to the primary functions of the plug, keep your eyes out for the three more added terminals. As a bonus, they offer three more terminals for electric brakes, reverse light, and 12V hot lead.
7-way trailer wiring color code:
First, we’ll examine the conventional color scheme for 7-way wiring harnesses. After that, will dive into the detailed instructions. With this color scheme, connecting the wires later would feel as easy as it ever gets.
Different industries use different color codes to wire harnesses, which might be confusing. For example, the wiring standards used by the RV industry deviate from the ones used by the SAE (Society of Automotive Engineers). Here’s the rule of thumb for both:
Traditional SAE color code:
| Color | Function | Minimum Wire Gauge Needed | Where to connect (vehicle side) | Where to connect (Trailer side) |
|---|---|---|---|---|
| Green | Right Turn/Brake Light | 16 | Vehicle’s wiring harness – right turn | Trailer’s right turn signal |
| Yellow | Left Turn/Brake Light | 16 | Vehicle’s wiring harness – left turn | Trailer’s left turn signal |
| Brown | Tail/Running Lights | 16 | Vehicle’s wiring harness taillight | Trailer’s taillights |
| Blue | Brake Power | 12 | Electric brake control power output | Trailer’s brakes |
| Red/Black | Battery Hot Lead | 12 | Fuse block or FUSED battery lead | Breakaway kit, interior lights, or battery charger |
| Purple | Reverse Lights | 16 | Back-up circuit of vehicle’s wiring harness | Back-up lights/ hydraulic coupler |
| White | Ground | 12 | Vehicle ground point – uncoated metal | Trailer ground point – uncoated metal |
Note: Different colors may be applicable. Connectors should be tested with a circuit tester.
RV color code: 7-Way Trailer Wiring Color Code (RV Standard)
| Color | Function | Minimum Wire Gauge Needed | Where to connect (vehicle side) | Where to connect (Trailer side) |
|---|---|---|---|---|
| Green | Tail/Running Lights | 16 | Vehicle’s wiring harness – right turn | Trailer’s right turn signal |
| Yellow | Reverse Lights | 16 | Vehicle’s wiring harness – left turn | Trailer’s left turn signal |
| Brown | Right Turn/Stop | 16 | Vehicle’s wiring harness taillight | Trailer’s taillights |
| Blue | Brake Power | 12 | Electric brake control power output | Trailer’s brakes |
| Red | Battery Hot Lead | 12 | Fuse block or FUSED battery lead | Breakaway kit, interior lights, or battery charger |
| Black | Battery Hot Lead | 16 | Back-up circuit of vehicle’s wiring harness | Back-up lights/ hydraulic coupler |
| White | Ground | 12 | Vehicle ground point – uncoated metal | Trailer ground point – uncoated metal |
Note: Different colors may be applicable. Connectors should be tested with a circuit tester.
Minimum Wire Gauge:
The industry standard minimum wire gauge is 16 gauge for the reverse light, brake lights, turn signals, and the running lights of a 7-way trailer plug. On the other hand, experts suggest, a 12-gauge minimum for the battery hot lead, brake power, and the ground.
Steps for Wiring a 7-Way to a Trailer:
With an understanding of the functions of each wire, we will now go over the specifics of how to wire a 7-pole connector onto your trailer.
Connecting the trailer side:
1. Get your trailer’s wiring ready to be installed.
To begin, gather all the tools and supplies you’ll require to wire the trailer.
- A wiring enclosure (junction box) to keep cables in place and out of sight;
- To deal with a detached trailer, a breakaway kit;
- A braking system regulator for use with trailers;
- Trailer lights, or a full trailer light kit to replace any number of lights on your trailer. It will come with all the needed wiring.
Before installing new bulbs, remove the old ones. Using a 7-way harness is sufficient if you are not changing any of your lights.
2. Find or set up the junction box:
Find the junction box (it’s usually in the trailer’s front) and take off the cover if you need to replace the wiring in your trailer. Then, take the terminal nuts off.
On the other hand, a new junction box Installation requires finding a suitable position. For instance, the trailer tongue’s inner edge. Put the box close enough to each wire. But, to avoid interfering with other components, put it away from the rest.
If you don’t prefer a junction box, you may still use the updated wiring harness to connect its electrical components.
3. Hook Up the Trailer:
Connecting with the junction box:
First, take off the nuts from each stud in the junction box. This is only necessary if you are installing a brand-new 7-way connector. If you have to replace the wire, unscrew all the junction box terminals, and get rid of the old wiring.
To install your new cable, you must first remove any excess insulation and cut the wires to the proper length. Connect ring terminals to the new wires by crimping them into place. In the junction box, connect the terminals to the appropriate studs.
Put the nuts back on when you’re done. Use wire clips to tuck away any stray wires.
Connecting without the junction box:
Instead of a junction box, you can use a heat gun and butt connectors to join the new 7-way to the old wiring.
Use wire clips to tuck away any stray wires.
WARNING: Before attempting any wiring, be sure to consult the wire harness’s manual. Each wire’s purpose will be specified in the manual. In some cases, matching wire functions by color alone won’t be enough.
Connecting the vehicle side:
The next step, after attaching the trailer, is to wire the vehicle. So, here we go:
1. Get your vehicle ready for installing wiring.
With a 7-way connector:
You are in luck if your car has a 7-pin plug already! The trailer is ready to go as soon as the automobile connector is plugged into the trailer.
Installing with a 4-way connector:
If your vehicle comes equipped with a 4-way connector, you only need an adapter kit. We recommend using the ETBC7 kit. The ETBC7 is a complete adapter kit that comes furnished with every piece of equipment necessary for making the upgrade from a 4-way connector a breeze. So, change your vehicle’s 4-way connector into a 7-way using this kit.
Use a circuit tester to make sure your car’s wiring is working properly before hooking up. Turn on each light at a, and look at the circuit tester for a matching signal to confirm you’re using the correct wire.
Installing without any connector:
If your car doesn’t have any connectors, you can still get a 7-pin plug by swapping in a 4-pin one with an adapter. What you need here is a clear understanding of how to wire a four-pole connector.
If you need to clamp or splice wires together for any reason, make sure you double-check their operation first. First, make sure you know what each wire is for. In this regard, consulting your vehicle’s manual or a circuit tester would help.
In most cases, the area behind the taillights in the trunk is where a circuit tester can be plugged in to access the car’s electrical system.
To verify that you are using the correct wiring, try turning on each light individually and look at the circuit tester for a matching signal.
2. Connect Vehicles:
A vehicle’s wiring harness will connect to the pre-existing bulbs in one of the three ways.
- Plugging in;
- splicing into;
- clamping onto.
The availability of a specific connector type in the vehicle model will determine your choice. Following this brief overview, we’ll go into the particulars of each step.
Just a few pointers and reminders:
- Mounting brackets can be used to secure the connector to the vehicle if it is located under the automobile. Doing so will lessen the likelihood of damage from the connector dangling.
- You may avoid corrosion by applying a thin layer of grease to all of your car’s electrical connections. Apply it to the plugs and the connectors.
3. Plug adapters, 4-way to 7-way:
In order to connect the battery cable to the trailer’s brakes, you’ll need an adaptor that fits into your standard 4-way plug. Following the adapter’s insertion into the pre-existing 4-way, a further connection of the three wires will be necessary.
Your vehicle’s electric brake control will receive power from one of these lines (usually blue but so often black).
Extra wire and butt connections will lead a different colored wire (usually red or black) to the battery’s positive terminal.
Never connect wires without first testing their functionality with a circuit tester.
4. Plug-In connection:
Some automakers “pre-wire” vehicles so that cables are easy to connect. These connectors attach to the vehicle’s wiring without splicing or cutting.
Usually, the plug-in port is situated close to the back of the automobile, either behind the taillights or the paneling.
Concluding the connection:
After hooking up your trailer’s wiring to your vehicle’s system, plug the trailer and car together to test the wiring and ensure everything is working properly. If necessary, make corrections. Nothing to worry about if the lights come on at the appropriate times.
FAQs about 7 way trailer wiring diagram with brakes:
Is there polarity on electric trailer brakes?
When it comes to electric brakes, the magnets that you get in trailers are polarity neutral. So, you don’t have to worry about magnet polarization. During installation, it doesn’t matter which wire you connect to the brake signal and which wire you connect to the ground.
Is there a left and right side for trailer brakes?
Yes, there are. We can identify a left-hand brake with a left-curved magnet actuating arm. On the other hand, a right-curved magnet actuating arm indicates a right-hand brake.
What happens if you put trailer brakes on the wrong side?
Reduced braking performance and increased wear on the brakes might result from having one set of brake components on the wrong side.
Can you pull a trailer that has trailer brakes without a controller?
No, it is not safe to tow. Towing a trailer that relies on electric brakes requires a brake controller.
Final Words:
So, to conclude it all up, it is not an overstatement to say that you don’t have to be a trained electrician to wire your trailer. With a 7 way trailer wiring diagram with brakes in place, it is a fairly easy task to accomplish.
Following this guide, you’ll have no trouble getting your trailer wired for 7-way plugs. So, get ready to go in no time at all. If anything still bothers you, it takes only a few seconds to leave a comment, right?