hi. i have an 05 dakota and purchased the spliceless trailer light harness from dodge and installed it and all works well except one thing. the flat 4 plug works just fine but the 7 way round does not. when i was installing the harness their was a blue wire towards the end of the harness that connects to the battery that i didnt know what to do with. the instructions were pretty much useless and i dont know if that could be the cause of my problem. any help would be great. thanks

 

Yeah that could be a source of your problems, or there could be an incorrect ground somewhere else, I've never installed a trailer harness before but working with electronics on my truck all the time it might be a good idea to find a route to run the wire to the battery. Get a 1/4-3/8" battery terminal (12-10AWG) from your local hardware store, connect the blue wire to that and that to the battery. If you need help finding a route to run the wire I'll go outside, look around and take pics after I find a route.

 

I'm not sure if these sites will help but I'll pass them on to you. They deal with trailer wiring from the trailer's point of view and the wiring is industry standard for the connectors ( 4 pin, 6 pin, 7 pin )

Trailer Wiring
RV Tow Vehicle
RV Wiring
Hitch and Trailer

I thought I had a link for a Dodge diagram but this is all I have. Hope it is some help.

Jimmy

 

the blue wire needs to be hooked up. it is for a trailer brake system, most small utility trailers dont need the braking system but if you go with a car trailer thays what its for

 

thanks for all the input. i spoke with someone at dodge and they also said that the blue wire is for a brakeng system but for my application i dont need that so ill worry about that some other time. as for the 7 way round not working it was a loose connection in the harness and once that was fixed all worked well. thanks again.