Ok, some background. I have an 18' flat trailer. I have been using a '98 Dodge Ram to pull it. Both the Dodge and the trailer were already wired and the wiring was compatible....everything worked. I bought the Dodge and the trailer separately from different seller. The trailer was professionally built by a local builder and the Dodge wiring is factory. The only addition I made was to add a digital brake actuator to the truck. That worked, too.Now I have this '98 Chev 3500. It has a factory trailer wiring harness in place, but not finished. The harness is just stuffed up under the bumper. The owner's manual says to wire it up to the aftermarket socket connector of my choice. I bought a black plastic (Pollack) receptacle, the kind that has one socket in the center and 6 other sockets surrounding it in a circle. That's because that's the type of connector on the trailer. Looking at the lugs of the new receptacle, they are labeled (clockwise): 3GREEN, 5RED, 1WHITE, 2BLUE, 6BROWN, 4BLACK. The center lug is not labeled. Looking at the trailer connector, it is labeled the same as the truck connector, only counter-clockwise (so they match up). However the wire colors do not match up with the lug labels. A green wire is attached to the lug labeled brown, a black wire is on the blue lug, white wire on white lug, yellow wire on red lug, brown wire on green lug. The lug labeled black is empty as is the center lug. Also, there is a red wire, but it has been purposely cut shorter than the others and is not attached to anything. Now we move to the truck wires. There is a harness with 5 wires (dark green, light green, brown, yellow and white). The white wire is heavier gauge than the rest. In addition, there are 2 more heavy gauge wires, blue and orange, coming from the rear of the left frame rail. The owner's manual says to connect them as follows:
Brown: rear lamps
Yellow: Left stop/brake light
Dark Green: Right stop/brake light
White: ground
Light Green: backup lights
Blue: Electric trailer brake circuit
Orange: Fused auxiliary circuit Now my questions:
1. Isn't there some sort of standardized way to wire things like this?
2. Was it just pure chance that my Dodge wiring matched the trailer wiring....especially with most of the trailer wires not matching the colors labeled on the lugs?
3. With no blue wire on my trailer wiring, why did my electric brakes work? Are my trailer brakes really the black wire that's attached to the blue lug?
4. What is the red wire for? And if standard trailer wiring includes a red wire, why no mention of a red wire on the truck side?
5. What is supposed to go on the center lug? Is that where the big fat white ground wire goes? If so, why isn't there a wire connected to the center plug of the trailer connector. Is it because the trailer wiring is grounded to the trailer frame rather than back through the truck wiring? The white wire on the trailer connector is just a standard gauge wire (12 or 14) and I have a hard time believing that's supposed to match up with the big fat ground wire on the truck.
6. Both receptacles have lugs labeled "black". So why no black wire in the truck's factory trailer wiring harness? Same deal with red. There are lugs labeled red but no red wires in the truck harness. I'm assuming that some of these lugs and wires are not being used because this is just a car hauler trailer, not a travel trailer, therefore no need for a charging circuit to charge a trailer battery, run a fridge, etc. Also, I don't think my trailer has backup lights. But I'd like to wire this up correctly so that if I ever had to tow a travel trailer, everything would work correctly. I'd really like to come close the first time rather than a total trial and error approach. Should I just put power to each trailer wire in succession and see what comes on? Any help or tips will be very appreciated.
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