7 Pin Trailer Wiring Kit With Electric Brakes

Understanding what each pin does will allow you to pinpoint any problems in your
setup and rectify them quickly and efficiently.

Note that an adapter can help connect a 7-pin to a 4-pin vehicle, however you will
lose functionality such as reverse lights and electric brakes.


A trailer plug features seven pins for multiple purposes. While its first five wires
(lights, grounding, left turn signal and right turn signal) are generally utilized, its fifth
(blue) wire may also be utilized for electric trailer brakes or surge hydraulic brakes
on some boats and horse trailers.

Rewiring your trailer requires the use of proper techniques in order to protect its
wires and connectors from damage. Soldering is usually considered the ideal
approach, ensuring a strong, dependable connection; however, when dealing with
old wiring or replacing damaged plugs this may not always be possible – in such
instances butt connectors and heat guns should be utilized instead.

Test your work regularly if you are new to electrical projects, particularly if the
electrical aspect is unfamiliar to you. To do this, ask someone else to operate the
lights from the trailer end (depress brake pedal and activate turn signals) while you
probe each pin with a digital multimeter and verify they all read 12v+ when running
trailer while reading 0v+ when not.


Every trailer uses electricity for lighting and braking systems that operate using 7
pin trailer plugs as the connecting point for this power source. In order for this plug
to function optimally, all wires must be securely inserted in its socket.

When opening up the junction box that connects your vehicle’s 7-pin trailer
connector, there will be seven connection ports. Note that their wire colors do not
correspond – what matters is how each wire functions!

No trailer should be without lights! In addition to lights, many trailers feature a 5th
pin for auxiliary power and blue wire that activates their brakes when backing up
their car. An ohmmeter will help confirm that all wires are connected properly and
functioning as designed; 16 gauge is recommended as minimum gauge.

7 Pin Trailer Wiring Kit With Electric Brakes

Connecting the Wires

If you don’t own a junction box, an adapter can make upgrading from 4-pin to 7-pin
trailer plug easy and inexpensive. Our ETBC7 kit contains all necessary connectors
and wires. First locate your vehicle’s junction box (usually under its rear bumper).

Remove any existing wiring from the old 4-pin connector and connect new wires to
the trailer plug’s seven pins using butt connectors or crimp rings. Connect ground
and brake wires directly to their terminals in the junction box (ground-to-ground and
brake-to-brake respectively), using clamping cables if necessary; any extra wiring
may be secured using wire clips.

Important to keep in mind when choosing a 7-pin trailer plug is that it does not
control your brakes directly; rather, a brake controller must still be used. But it does
add a fifth wire for powering backup lights and 12-volt auxiliary wire. Furthermore,
knowing each of the standard trailer wire colors helps, but don’t rely solely on them matching.


Testing after you’ve finished wiring can help ensure everything worked as planned
and get you back on the road quicker if any issues arise. A few simple tests can
quickly pinpoint issues and help get back onto the road as soon as possible.

Assuming your multimeter has test leads that correspond with its colors (black is
negative and red positive), connect one end of these to a battery or jump box and
the other to a ground pin on your vehicle receptacle; using black as negative and
red as positive can make this task simpler.

Set your multimeter to read amperage. Touch one of its probes directly to the wire
leading from the brake magnet – typically green or brown in color – on which your
multimeter sits.

If the circuit shows high system amperage readings, that indicates an issue
somewhere in your trailer wiring system – be it a shorted brake magnet coil or
defective controller. As soon as brake magnets are disconnected from their coils,
system amperage levels will quickly decline – it may take multiple attempts before
getting an accurate reading.

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