In this section you will find information on legal requirements for trailer lighting, wiring diagrams for 4, 6 & 7-pole systems, as well as some lighting terminology. Some of the most basic maintenance practices can add years of service to your trailer lighting system. One tip is to always unplug the trailer harness from the tow vehicle before launching and loading. Doing so will prevent thermo shock failure when a hot bulb comes in contact with cold water. Another easy maintenance tip is to coat all exposed metal surfaces with dielectric grease, including trailer harness plugs, bulb sockets and contacts. The grease will help prevent corrosion, which is the leading cause of light failure. Finally, as a safety precaution, always check the trailer lighting for proper operation before heading out on the road.
 I. LIGHTING REQUIREMENTS

Function

Color

Visibility Requirements
1 Tail Light Red 45 Degrees Left and Right
10 Degrees Up and Down
2 Stop Light Red 45 Degrees Left and Right
10 Degrees Up and Down
3 Turn Light Red 45 Degrees Left and Right
10 Degrees Up and Down
4 Rear Reflex Red 20 Degrees Left and Right
10 Degrees Up and Down
5 Rear Sidemarker Red 45 Degrees Left and Right
10 Degrees Up and Down
6 Rear Side Reflector Red 20 Degrees Left and Right
10 Degrees Up and Down
7 Front Sidemarker Amber 45 Degrees Left and Right
10 Degrees Up and Down
8 Front Side Reflector Amber 20 Degrees Left and Right
10 Degrees Up and Down
9 License Light Clear Above or Side Illuminated
OVER 80" LIGHTING
10 Rear Clearance Light Red 45 Degrees Left and Right
10 Degrees Up and Down
11 Rear Identification Light Red 45 Degrees Left and Right
10 Degrees Up and Down
12 Front Clearance Light Amber 45 Degrees Left and Right
10 Degrees Up and Down
Interpretations
A United States The front sidemarker must be mounted so that it is visible 45 degrees left and right without obstruction from the trailer or tow vehicle to comply with NHTSA's interpretation of "as far forward as practical."
B Canada The front sidemarker must be mounted from 39" to 60" from the front of the trailer and be visible from 45 degrees left and right without obstruction from the trailer and tow vehicle to comply with Transport Canada's interpretation of "as far forward as practical."
 
 
  II.   TERMINOLOGY:  
  OVER 80” TAIL LIGHTS - These units meet seven to eight DOT-108 lighting requirements when properly mounted. Seven function units meet tail lamp, stop lamp, rear clearance lamp, red side marker lamp, red side reflex reflector, and rear reflex reflector. The eighth function met is license illuminator.

UNDER 80” TAIL LIGHTS - These units meet six to seven DOT-108 lighting requirements when properly mounted. Six function units meet tail lamp, turn lamp, stop lamp, red side marker lamp, red side reflex reflector, and rear reflex reflector. The seventh function met is license illuminator.

OVER 80” SIDE MARKER LIGHTS - These units meet three DOT-108 lighting requirements when properly mounted. These functions are side marker lamp, clearance lamp, and side reflex reflector.

SUBMERSIBLE LIGHT - This design is not sealed or waterproof, it uses the “bell jar” concept. Air pressure builds up inside the light and does not permit water to come in contact with the bulb or socket. This can be explained by placing a glass upside down in water…the water only partially fills the glass.

WATERPROOF LIGHT - This design is completely sealed so that water can not come in contact with the bulb or socket, at any angle, when the light is underwater.

 
 
 
  III.   4-WIRE SYSTEM WIRING DIAGRAM

SPECIAL TIPS

Avoid routing wires over sharp edges or pinching them. All splices should be sealed with flexible-waterproof calking for extra protection.
 

 
 
  IV.   6-WAY & 7-WAY CONNECTOR WIRING DIAGRAM  
 

 
 
 
  V.   MAKING A SPLICE CONNECTION