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Various connectors are available
from four to seven pins that allow for the transfer of power for the lighting as well as auxiliary functions such as an electric trailer brake
controller, backup lights, or a 12V power supply for a winch or interior trailer lights. Choose a connector that has the required number of pins for
the functions required for your trailer. If the connector is under the vehicle, you will want to use a
mounting bracket to attach it to the vehicle.
This will help prevent damage that may occur if the connector is left dangling.
4-Way connectors are available allowing the basic hookup of the three lighting
functions (running, turn, and brake lights) plus one pin is provided for a ground wire. Most standard light duty trailers will use a 4-pole flat
5-Way connectors are available allowing the basic hookup of the three lighting functions
(running, turn, and brake) and, besides the ground, one pin is available to provide support for another function. Typically the 5-Way Flat is used for trailers
with surge brakes or hydraulic brakes. The additional wire is tapped into the backup lights to disengage the hydraulic trailer coupler (actuator) when the vehicle
is reversing, thus turning off the trailer's brakes.
6-Way connectors are available allowing the basic hookup of the three lighting
functions (running, turn, and brake). The ground and two extra pins are available to provide two additional functions, typically for electric brakes
and 12 volt "hot" lead. The 6-way round connectors are very common on horse trailers. The 6-way square connectors are more common on
Note: In some applications, the black battery power connection and the blue brake controller
output connection are reversed.
Aside from the three main lighting functions, additional pins for electric brakes, a 12 volt "hot" lead, and backup lights are
available. There are two types of 7-way connectors. One has flat pins, which are often referred to as blades. The other has round pins. The round pin
style is very rare. The RV style 7-way with flat pins (or blades) is very common. It is often found on newer trucks and SUVs that come equipped from
the factory with a trailer hitch.
Note: To ensure that your trailer connector is wired properly, we recommend using a circuit tester to match pins by function. Because wire colors can vary, they are not as reliable for determining functions. And improperly connected wiring can cause damage to electric components.
Often the 4-pole trailer connector will remain in the trunk or cargo area of a car or SUV when not in use. This helps to extend the life of the connector by protecting it from the elements and accidental damage. When it is needed for towing, simply pull the connector out and shut the trunk or rear door. The rubber weather strip that provides a door seal keeps the wire from getting pinched. If the trailer connector needs to be mounted under the vehicle, we offer many different mounting brackets that will help to protect the connector and keep it from dangling beneath the vehicle.
The T-One connectors and hardwire kits all use a 4-pole trailer connector. This connector is most common among the smaller utility trailers and can easily be adapted to match the larger 5-pole, 6-pole and 7-pole styles. Using an adapter lets you avoid having to splice into the vehicle's wiring system. Adapters will plug into the flat 4-pole connector and have wire leads to provide additional functions such as powering trailer brakes, power lead for utility lights, reverse, or auxiliary power for a winch or tools. If your vehicle or trailer is equipped with something other than a 4-way plug, such as the larger 7-way round plug, you can use our adapter fitguide to find the one that is right for your vehicle and trailer.
If you have a Modulite (powered converter), Converter, or T-One connector that is not working properly, you need to use a circuit tester to determine the source of the problem.
When too many amps are drawn through the converter box, it can be shorted out. The possible causes are:
If you find some, but not all, lighting functions work properly you may have a ground problem. In this situation a weak ground is just strong enough to provide some lighting functions but not all. When the taillights and brake lights are used at the same time, it creates the maximum amp load of the lights on the trailer. If a ground problem exists, it will show at this point. The places to check grounds are as follows:
NOTE: If you purchased your wiring harness from etrailer.com and none of these fix your problem please feel free to contact us so our product experts,
and installers can determine possible remedies or warranty coverage.
By law trailers are required to have at least running lights, turn signals, and brake lights. To provide the power and a connection for these functions, the tow vehicle's electrical system needs to be tapped into. There are two options available for connecting to your vehicle's electrical system, a plug in style T-One connector or a custom selected hardwire kit.
The easiest way to make this connection is with the use of a T-One Connector, which comes with OEM style connections that simply plug into your vehicle's existing wiring harness, typically near the rear of the vehicle or by the tail lights. Sometimes the vehicle manufacturer will run the wires to an easily accessible plug underneath the vehicle or behind the paneling in the back cargo area. T-Ones come pre-wired with a 4-way flat trailer connection and can be expanded to 5-way, 6-way, or 7-way trailer connections through the use of a wiring adapter.
If a T-One is not available, a connection can still be easily made by using one of our custom selected hardwiring kits. We offer kits with all the pieces you will need to simply tap into the existing wires on your vehicle. This may sound difficult, but quick splices make installing the wiring harness quick and easy. A quick splice has two grooves in it; one groove is for the vehicle wire, and the other groove is for the wire on hardwire kit. Once both wires are in the grooves, you simply press down on the top of the quick splice. This forces a metal piece into both wires, connecting the circuit and eliminating any need for cutting or splicing. To hardwire the tow vehicle for a trailer connector you need to locate the proper wires. To help in this task you can check the vehicle's owner manual or use a circuit tester. The circuit tester is used to make sure the correct wires on the hardwire kit are connected to the matching wires on the vehicle; it helps determine which wire performs which function. The easiest place to tap into the vehicle's wiring system is behind the tail lights. By turning on the left turn signal, a circuit tester can be used to test the different wires behind the driver's side tail light. When the circuit tester lights up, you know that wire carries the left turn function. A quick splice slid through the yellow wire on the trailer connector and around the just found vehicle wire will clamp down to provide a secure connection.
Vehicle manufacturers have intermittently changed wiring colors over the years.
It is recommended that a circuit tester be used on the tow vehicle's wiring harness to verify that the correct wire has been located for the proper function.
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