Wiring For Trailer Lights

Many Ranger owners have step bumpers with towing capabilities or have added a hitch.  Let’s face it, if you own a truck, sooner or later you’ll find yourself needing or wanting to tow something.  Most small trailers use a 3-prong plug.  It includes the ground, taillight, and stop/turn signal connections.  When you look at the rear underside of the bed there is a wiring harness with a plug at the left rear end of the frame.  The wire is in plastic tubing and splits off to the left and right taillights.

Left Side:

If you look in the wiring going to the left you will find a Light Green wire with an Orange stripe.  This is the wire for the left stop/turn signal light.  You will also see a Brown wire which is the taillight wire.

Right Side:

If you look in the wiring going to the right you will find an Orange wire with a Light Blue stripe.  This is the wire for the right stop/turn signal light.  You will also see a Brown wire which is the taillight wire.

Your new harness will tell you which wire is for what.  Just wire the appropriate wires to the ones described above and then wire the ground to a good ground at the frame.

The Law:

By law, trailer lighting must be connected into the tow vehicle’s wiring system to provide trailer running lights, turn signals and brake lights. This is accomplished by tapping into the tow vehicle’s electrical harness to transfer power to the trailer wiring system. Connectors are used between the two to allow disengagement when not towing.

Connectors:

Various styles of connectors are available with four to seven pins to allow transfer of power for the lighting as well as auxiliary functions such as electric trailer brake control, backup lights etc. Choose a connector that has the required number of pins for the functions required.

The male end is mounted on the vehicle side and the female on the trailer side.

Dual Purpose Bulb System
Wire Function Wire Color Ford
Right Turn & Brake Lights Green Orange w/ Blue Stripe
Left Turn & Brake Lights Yellow Lt Green Orange Stripe
Tail Lights Brown Brown
Ground White Black or Grey
Single Purpose Bulb System
Brake Lights Use Converter Red w/ Green Stripe
Backup Lights Red Black w/ Pink
Electric Trailer Brakes Connect To Blue Wire From Brake Controller

 

Trailer Connector Samples:

 

4-Way Trailer Connection:

4 way flat molded connectors allow basic hookup for three lighting functions;  turn signal / stop light (green),  turn signal / stop light (yellow), taillight / license / side marker (brown) and a ground (white).

 

4-Way Connector (Trailer End)

4-Way Connector (Vehicle End)

4-Way Connector (Trailer End)

4-Way Connector (Vehicle End)

5-Way Trailer Connection:

Same as 4 way system listed above but adds a extra blue wire for brake signal or auxiliary power.

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.

5-Way Connector (Trailer End)

5-Way Connector (Vehicle End)

5-Way Connector (Trailer End)

5-Way Connector (Vehicle End)

6-Way Trailer Connection:

Round 1 1/4″ diameter metal connector allows 1 or 2 additional wiring and lighting functions such as back up lights, auxiliary 12v power or electric brakes. Note: The black (sometimes red) 12v and blue electric brakes wire may need to be reversed to suit the trailer. Check with a test light or VOM. Uses: horse trailer, travel trailers, landscaping trailer, car trailer, etc.

5-Way Connector (Trailer End)

6-Way Connector (Vehicle End)

7-Way Trailer Connector:

Round 2″ diameter connector allows additional pin for auxiliary 12 volt power or backup lights. Uses: heavy duty landscaping trailer, car trailer, boat trailers, horse trailer, travel trailer, construction trailer, etc. Check with a test light or VOM.

7-Way Connector – Flat Blade (Trailer End)

 

7-Way Connector -Round Pin (Trailer End)

7-Way Connector – Flat Blade (Vehicle End)


7-Way Connector – Round Pin (Vehicle End)