Trailer wiring

[2500ctd]

Somewhere in my big book of projects, I need to redo the wiring on my car trailer. Just a plain old 18' hauler. I know the wiring schematic, just looking for ideas on execution. Not sure if I want to add a breakaway switch or not. I probably should. One idea is to put a 7 way connector on the trailer like the truck and have a doulbe male ended patch cord to connect the 2. No hanging wires to catch. If I get 7 conductor trailer cable, I basically have to cut the jacket off at the axles to pull the brake wires out then just run the remaining wires for the lights. Or I could get a parallel pair for the brakes and the 4 conductor wire for the lights. I might also need a 7 stud junction box on the tounge as well, if I do the female connector on the trailer as well. Any suggestions? Want to keep it simple so trouble shooting is easier as well. I have had this thing for about 15yrs and its finally time to fix the wiring, and make it last another 15. Interesting how I never had any issues with it till I loaned it out. Now if someone needs it I will do the pulling. lesson learned.

[stodg73]

The 7 wire cable is fairly expensiveI bought 30' and it was $100. I wired up my 16' tandem flatbed wth it. My dad pulled it the next day and cut the new cable in half. So, make sure that you put the wiring where it won't get caught/pinched. It does become a pain that you have to cut the jacket off, just do it right the first time and you wont have any problems. My suggestion for your application would be to get the double 4 wires. This way you can put the wires together in a loom and then split them where you need too. I also like the double male end idea with no hanging wires. This would be a cheap repair if it got cut or damaged.

[flagmanruss]

Personally, I dislike wiring which runs through the trailer frame... steel horse trailers are known to have huge problems with frame rot & still manage to chafe wires on occasion. (One fabricator I know used closed box and welded the ends closed, except for a plug at each end... he poured oil into the frame & it sure as hell has not rotted out!) I much prefer plastic conduit secured underneath. I'd run wired pairs. A double male pigtail will be confusing because the wiring will be reversed. I have a M/F 24" extension harness I use when needed. The trailer tongue has a bit of extra wire secured with 2 zip ties... but not clamped so hard that I could not work a few inches of wire in/out if I needed. I use a bungie between the truck & trailer to hold the exccess off the ground on a bumper tow... only once, I apparently hooked the hitch with the wires, backing out at my destination... it pulled the plug out which was destroyed dragging on the ground. I built a socket into the side of my truck bed for a gooseneck connection... Rather than cut into the OEM wiring, (I could not find a T tap like my old trucks used) I have a male end which plugs into the OEM trailer socket... essencially an installed extension.) I use insulated M/F crimp connector at the lights, so they can be replaced without shortening the wires. You could use a barrier strip to bring everything together at the tongue, maybe even in a project box if you want... or you can just splice. I got ambitious & soldered these, used liquid tape to waterproof, then taped & finally covered with chafe protection. I rewired my old horse trailer... I used all signal-stat lights (bought them all & got a break on the cost). The cheap lights were just such a PITA... I still see my old trailer (new owner works with my brother) & 5 years in, he's glad I bought quality lights.

[2500ctd]

Thanks. What about have both a 4 way connector and a 7 way? My ramcharger only has a 4 way, and of course the Ram have the 7 way. I also looked at the traielr closer for ideas, and forgot this one has the brakes running one side and the lights split and ran down each side of the trailer. I will probably follow that but run the brakes split as well. That way no wires cross under the trailer. The trailer has little "U"'s welded to hold the wire up. Thinking of using adel clamps. instead. Seen people use pvc pipe to run the wires in as well. The trailer has angle iron for the main frame. 1/4 thick 4x4 iirc. Ideas on something to run the wires in? I had one cargo trailer lose half the rear ligths when a tire blew and caught the 12" of wire in the back where it came out of the frame to cross to the other side. That trailer has "C" channel welded together to from a tube. At 33' long I cant rerun the wires in the frame. :banghead: That one is getting sold however. When is a breakaway box required? Trailer only has one axle with brakes but changing that in the future as well. Only has dual 3500lb axles for now as well. One more thing, on the lights it states anything over 80" requires the 3 center lights. Is that 80" total? I would imagine so. Either way it doesnt have them and I want them so I can see the corners at night. Just wondering if that are required as it didnt come with them either.

[stodg73]

You can use electrical conduit from a hardware store to run the wires in to protect them, just use the clips and bolt them to the frame. Also, for you long trailer, the 33', you can use a wire fish to get the wiring where you need it. I have one of my trailers wired up with both a 7 way and flat 4, that way anyone can pull the trailer. The flat 4 has no brakes though. On the lights, I think it is total width, from the outside of the tire to the outside of the tire. This way you will be legal no matter what. Now, if the trailer was mass produced and it didn't come with lights, then you probably won't need them.

[MnTom]

With a trailer that size you are required by law to have brakes on it along with a break away system to apply the brakes. The seven wire cord you are looking at is about $2.50 per foot around here at an RV dealership. You could just put an electrical box somewhere on your trailer tongue for the receptacle and then run wires for the different functions from there. Standard RV cords have TWO #10 ga. (bat. +&-), ONE #12 ga. (brakes), and FOUR 14ga. (lights & aux.) wires in them.

[flagmanruss]

My horse trailers & campers have always needed brakes & came with them. The single axle landscaper's trailer came with the clearance lights (3 center) but no brakes. I guess not required at the rated load weight (does anybody ever pay attention to the rating on these?)... God only knows how heavy we were hauling hay but it was a slow speed trip & truck brakes were more than adequate. My trucks have long used the 7 flat prong RV plugs. The landscaper's traler came with a flat 4 pin plug & I just used the adaptor (until I dragged it on the ground & wrecked it). So I built a short adaptor pigtail. I've been replacing the lights on the landscaper's trailer with better grade truck lights as they fail. I like the DOT tape & use it liberally on all my trailers... left the graphics off the horse trailer when I bought it in exchange for DOT tape. If someone hits my trailers I want them to feel really stupid.

[2500ctd]

With a trailer that size you are required by law to have brakes on it along with a break away system to apply the brakes. The seven wire cord you are looking at is about $2.50 per foot around here at an RV dealership. You could just put an electrical box somewhere on your trailer tongue for the receptacle and then run wires for the different functions from there. Standard RV cords have TWO #10 ga. (bat. +&-), ONE #12 ga. (brakes), and FOUR 14ga. (lights & aux.) wires in them.

On my 18' car hauler, brakes are required? Did not know that. It has one axle brakes and they do a good job. I do keep those maintained. I found one place that sells 25' of flat 4 cord for $16. Might get 2 of em and run em down each side. When I put the LEDs on the trailer I used another 4 way connector to make them replaceable with out having to cut wires. With a harness down either side I can double up the wires not needed thus running 2 14ga wires in parrallel to power the lights. Poor man's way of heavier gauge wire. MAinly cause at $16 not worth buying a single roll of brown wire to maintain the color coding for the running lights, since I need a brown to run down both sides. This way I also get the 4 way connector at the lights well. They also sell duplex brake cable in 100' rolls for $70. At most I only need 25'. I figure roughly 12' down each side to the axles. Like I said trying to prevent wires from crossing the trailer underneath. This trailer gets dragged all over. My cargo trailer tends to stay on the road as it like to sink when loaded and not on the road.....yeah lessoned learned. Still trying to think of a simple yet damage proof setup to hook up to the truck.