Trailer running lights not working

Round 7-Pin Wiring Diagram

• ? White Ground.
• • Brown Taillights.
• • Green Right turn / brakes.
• • Red Auxiliary power.
• • Yellow Left turn / brakes.
• • Black Reverse lights.
• • Blue Electric brakes.

Trailer Wiring Diagram and Installation Help - Towing 101

Here ya go.

The 4-wire flat plugs usually have a white (ground), green (right brake/turn) yellow (left brake/turn) and brown (taillights - left and right). If your brake and turn lights work but the taillights don't, check the plugs (trailer and truck sides) for corrosion, and chek both the trailer and truck wiring harnesses for chafed insulation and bare conductors on the brown wires. Likewiae if the taillights work and the brake/turn lights don't, perform the same checks on those wires. And last but not least, be sure that the white wires (truck and trailer) are grounded well to the truck body and trailer frame.

check at the trailer connector on the truck. if you have every thing working there then its a wiring problem on the trailer and you will have to find the problem and repair.

Standard wiring colors are as follows:

4-Way

5-Way

6-Way

7-Way

Green

Yellow

Brown

White

Red

Blue

Purple

Right Turn & Brake

Left Turn & Brake

Tail Lights

Ground

Backup Lights

Electric Brakes

Auxiliary Power
Green- Right Turn and Brake
Yellow- Left Turn and Brake
Brown- Tail Lights
White- Ground
Red- Reverse (Back Up) Lights
Blue- Electric Brakes
Purple- Auxiliary Power

It sounds like your green and yello wires are shorted together somewhere along the length of the harness. I would check the wires on the trailer first. Easier yet, if you have another trailer to connec or access to another to use for testing, connect to it and see if the problem repeats; if it does the trouble is in the vehicle's wiring.

Use this as a guide and a 12 volt test light, or multimeter to see if power at proper terminal from truck. If power there, then connection at trailer plug, or wiring from there to tail lights on trailer is faulty.

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Trailer Wiring Diagrams 4 Way Systems

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

4 way tow vehicle side.
4 way trailer side.
5 Way Systems

Same as 4 way system listed above but adds a extra blue wire for brake signal or auxiliary power. Used on pop up camper trailers or utility / boat trailers.
5 way tow vehicle side.
5 way trailer side.
6 Way System, Rectangle Plug 3/4 inch by 1 inch 6 way rectangle connectors right turn signal (green), left turn signal (yellow), taillight (brown), ground (white). The red and blue wire can be used for brake control or auxiliary. Use on a small motorcycle trailer, snowmobile trailer or utility trailer. Can also be used as custom wiring on trailers with 3 light/wire systems. See "Tow Vehicle Taillight Wiring" below.
6 way tow vehicle side.
6 way trailer side.
6 Way Systems, Round Plug

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.

6 way tow vehicle side.
6 way trailer side.
7 Way Systems

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 RV flat blade tow vehicle side.
7 way RV flat blade trailer side.

7 way trailer lights:
Black- 12 volt (power)
Brown- tail lights
Yellow- Left turn signal
Green- Right turn signal
Blue- Brakes
White- Ground
Orange- Auxiliary power (not always used, but example would be trailer back up lights, if equipped

The basic 4-flat trailer wiring colors are as follows.
Yellow-Left turn/Stop, Green- Right turn/Stop, Brown-Running Lights and White-Ground
7-way trailer wiring colors are as follows.
Yellow-Left turn/Stop, Green- Right turn/Stop, Brown-Running Lights, White-Ground, Red or Black-auxiliary power, Blue-Trailer Brakes and Purple-Reverse lights

Trailer end; Red=Brake
Brown=Running lights
Yellow=Left
Green=Right
White=Ground
You will need a turn and brake signal box IF, you have different bulbs for brake and turn lamps. If the brake and turn bulbs are one(red)lens than no box will be required. Thanks, Dana