Home Forums Gear Hunting Trucks and Four-Wheel Drives Trailer plug wires

Christ I hate trailer wiring. In theory it's SO simple, but in practice it's such a PITA. I need to rewire my stock trailer, but before I did so I made sure the plug at my truck was working right. Sure enough it's not. It's a 2012 Ram 2500, with factory brake controller. Running lights, turn signals, and brake lights are all good to go, but the trailer brake post just gives a steady trickle. And when you turn the gain down to 0 no difference, and when you turn it up to 10 no difference. Doesn't matter whether you have the brake engaged or not. I took it to the dealer and they said it needed a "flash update" for the computer and that might fix it. I left thinking it had worked since they didn't phoucing say it hadn't. I checked again today before I dove in on the trailer, and it's doing the same damned thing.

I've read that the factory brake controller is a weak point on these trucks. WTF?

Can't help you on the truck end. But this page has sure helped me on all the other wiring.

http://www.etrailer.com/faq-wiring.aspx

On my '08 Dodge, the light wires ahead of the jack are only 18ga. If you plug in a trailer with a few extra clearance lights, that's putting a real strain on the watts.
I'm rebuilding a camp trailer now and it's getting all LED lights just for that reason.

A couple years ago, I replaced the light jack on the truck, too. The stock one gave me all kinds of fits. Before you spend a wad at the dealers, check the brake wire ahead of the jack to see if you have good power there. It could be a problem in the jack.

If it's bleeding power when you don't have pressure on the brake pedal, it's got to be in the brake controller. You will have constant full power to the controller but there should be none after it until you push the brake. Also, check the emergency brake pedal if it has a switch to set trailer brakes. It might be sticking slightly on, enough to give you a drain.

Thank you gentlemen.

Are you sure you should be seeing full voltage on the trailer brake when no trailer is detected and when the truck is not moving? I think the factory brake controller uses the vehicle speed sensor and other doodads to regulate applied voltage.

I hate em too....rare that all mine work, very rare.....

BGG-
Can you swap a borrowed brake controller to see if that's the problem?

I think I'd start there before redoing the trailer.

Good point. I do seem to remember reading something about that now that you bring it up.

Try the trailer on the road before doing anything expensive.

Can't help with the break controller, but if you're going to rewire the trailer, go with tinned 14 ga marine wire, sealed led lights, heat seal wire splices and run ground wires to the lights vs. using the trailer for the ground.

Yes, it'll cost more up front, but you'll save yourself all the grief of having to trouble shoot the trailer wiring every time you hook it up.

That sounds like a man talking from long experience!


Add me as another who hates trailer wiring! Would have thought things would be controlled by a wireless connection by now..

Agree with K1500. When testing voltage at the truck connector on my 98 Dodge, unless the brakes are engaged fully, I only get small voltage/amperage at the connector. If that brake magnet is engaged to the trailer wheel brake surface, you will not get it to pull any amperage.

[bleep] trailer lights/plugs all [bleep] suck [bleep] donkey balls.

Took the words out of my mouth.

I think I got the quote from Dan in Alaska's dad, but I'm not sure where he got it:

"In the beginning, man created the wheel. The trailer soon followed. And we've been trying to get the [bleep] trailer lights to work ever since."

There's an excellent treatise on this subject that's worth reading. It's titled 'Trailer Trials' by Pat McManus.

Gotta remember that one!!

Thanks for all the help guys. I'd never heard that stuff about the damned truck needing to be hooked to a trailer for the plug wires to work. What goat rope.

Trailer wiring just never works for me. I've rewired with cheap trailer wiring, old extension cords, heavy wires, I solder, heat shrink, and tape all the connections, ground each light, etc. Will work for a while, then inexplicable go kaput. But I have not ever put in the LED's before. I'll give them a go this time.

LED's alone won't cure your problems, good wire is a must

[img]http://i.ebayimg.com/00/s/MTYwMFgxNTEx/z/baUAAOSwDN1US~b7/$_35.JPG?set_id=880000500F[/img]

and sealed splices



and use some dialectric grease on the plug connection

I hate trailer wiring with a passion. Last fall I helped my dad troubleshoot the lights on his duck boat. He replaced nearly everything end to end and things still weren't working right. We diagnosed for 2 days with a meter and test light and basically rewired the thing tongue to tail only to have it not work. We reassembled everything just as he had originally installed it only to have it start working, we still don't know what we changed that fixed it. For what should be such a simple system they can be a real pain in the ass.

First thing you should do is determine if the trailer uses a ground through the connector or the trailer tongue. This can cause quite a bit of confusion and throw you off on your troubleshooting.

This link really covers just about every application out there.

http://www.etrailer.com/faq-wiring.aspx

I highly recommend using sealed splices instead of the cheap crimp type, if you have to use the crimp type put a piece of heat shrink over it to seal the splice.

Wrap the spliced area with some electrical tape and finish using a section of wire loom tied off with wire ties. That's how I always fix my trailer wires and it makes it look professional too.

use a soldering iron those crimp connectors suck in an area with vibration and movement. also the most important thing to start with is make sure the dang thing is grounded. espeically with those 4 flat style connectors. the white wire is ground nothing will work unless that is grounded.

Not very many trailers are grounded through the tongue anymore, and really that's a pretty poor way to ground the system. While the tongue-ball is a pretty secure mechanical connection it's not a very good electrical path, especially as you're driving down the road and the coupler is rattling/vibrating around on the trailer ball.

Grounding through the tongue is a terribly unreliable method, but it sometimes happens, regardless of the intention of your wiring. That is the source of a lot of intermittent trailer lights.

Could be worse - you could be dunking the whole thing in salt water a few times a week.

There's an easy fix if your trailer is grounded through the tongue, simply cut the trailer ground wire and extend it long enough to it's connector and connect to the ground pin. The truck/vehicle connector should already have a ground wire attached to it.

Dialectric grease is NON-conductive so it must be used right. The wires must have a very solid attachment or the grease can get between the wires and block the current flow. It works great to keep moisture out of the connector but can be counterproductive if it gets IN the connector.

If you want to pack the connector full of grease, there are conductive greases to use instead.

Trailer lights operate on the PFM principle.

Truckers carry a can of WD40 as standard equipment. A shot in the light plug cleans it out and gives good contacts.

Always had good luck using dielectric grease on Scully connectors, which use low voltage current through sensors and computer type devices.

As long as there's good metal to metal contact inside the connectors, dielectric grease won't affect them. However, if it gets between the contact points, it blocks the current. That's the nature of electricity and a non-conductor.

My truck started acting like it was possessed once. I was stumped. Hit the brakes and the mirrors would light up, turn signal would freak out the radio and wipers.....bizarre stuff. I found a bad ground and dusty trailer plug at fault. New trucks are VERY picky about the voltage feedback. Keep everything clean.

A bad ground can do some weird stuff.

Nobody has mentioned this so I will. It might help understand the strange things that happen when the ground is poor.

Current flows from Neg to Pos, not Pos to Neg. Electricity is the flow of negatively charged electrons which are stored in the Neg half of the battery. When a circuit is closed, they flow out through the ground wire, through the appliance, and back to the Pos post on the battery.
The ground on a vehicle is usually a battery cable bolted to the frame somewhere near the battery. All appliances are then bolted to the frame, too, either directly or indirectly. This is why, when attaching any electrical device to a vehicle, they tell you to disconnect the NEG battery cable, to neutralize the car body which is essentially hot all the time. Early cars had a positive ground system. Most of them switched in the '50's. I don't understand the chemistry here but they were having problems with the copper wire corroding with positive ground.

For the current to reach trailer lights, it has to flow through the entire car frame to the light plug, then through the trailer. There are miriad ways for the current to get blocked. That's why it's safer to run a special ground wire all the way from front to back, or at least through the trailer if your light plug on the car is grounded to the frame. It's to reduce the resistance from all the connections.

If there's a ground problem in the car, it can cause problems with all the appliances, not just the trailer lights. If a reduced current is all that can get through a dirty ground connection on the car, it will cause the current to be reduced on everything. If an appliance in the car isn't getting the full amps it needs to run because the trailer connection is syphoning off the juice, it can do some strange things in both the car and the trailer.
If the bad connection is on the pos side, it will only affect that particular appliance.

I'm just theorizing here because I don't really know. Note that many cars have the neg battery cable bolted to the engine, not the frame. That might degrade the connection when the trailer plug ground is connected to the frame. In that case, it might be better to run a special ground wire for the trailer all the way to the battery.

If the negative cable is attached to the engine then there should be a cable from the engine to the frame, that is all that is required.

drover

Direct ground from battery to engine is for the starter. It uses the most power of all electrical items. If all lights are grounded good to the trailer, a ground through the plug, and a good ground from plug to vehicle frame, you are 90% there. Most often ignored problem areas are in the back of the plugs themselves. Solder the ends of the wires, put them into clean sockets, and pack with dielectric grease.

And NEVER use those damned crimp on scotch lock splices.

Like I said before, use the dialectric grease on top of and outside the socket to keep water away but don't get it IN the socket. If it works it's way between the wire and the socket walls and screw, it will block current flow because it's non-conducting.
Used on the outside of the sockets, it will help prevent shorts by preventing current bleeding through dirt from one socket to the others.

I hear you cluckin big chicken, but what I meant was the inside of the plug before you put it back together. Not the male to female contact surfaces, but the internals to seal out the moisture. Smearing it on the outside just collects dirt.

Here, after you have made all your connections.



Not here.

FWIW I guess the truck WAS fine. Must've needed a trailer plugged in for the trailer brake wire to energize. I rewired the trailer and it worked just fine. Just in case anybody runs into the same issue, figured I'd post the resolution.

It took me a couple of days chasing ghost before I realize the same thing years ago so don't feel bad.

It can be a head scratcher when you're installing a new light plug on the truck. 'I KNOW this dang thing worked yesterday!'

Electricity is magic. Ever since I was little and saw my sister stick a fork in an outlet I have thought so, and nothing I've seen since and shaken that belief. Inexplicably things that should work sometimes don't, and things that shouldn't work sometimes do. It's easier to accept when I realize it's simply above my pay-grade to understand.

I had a trailer with the old 6 pin small round plug, and then bought a new trailer with that bigger 7 pin plug. However, I still had a big 22 ft gooseneck flatbed with the old style plug. So I had a little converter jumper that went from the 6 pin my truck to the bigger 7 pin plug. Every year , I tore my hair out trying to find out why sometimes the lights worked, sometimes the brakes worked, then other times nothing on the flat bed. Turned out those darn little mud wasp, got into the female end of the plug, laid eggs, and back filled with mud. I wasn't clever enough to see the plug wasn't going in all the way. I guess sometimes the mud feel out, some times it didn't. I finally found it when I took the female connector apart and saw the contacts pushed back into the housing.

I took all those old type connectors off and replaced with them all with the new versions and now I keep plastic bag on all the trailer connectors when not in use.

trailer wiring is about as simple as it gets. a hot to each light and a ground. a kid could wire one.i don't understand. for 30.00 you can put a complete kit on most any trailer.they even come color coded so you can't screw it up.

Trailer lights and trailer brakes are two differnt things.OP was having trouble with the brakes.

Yes, they are simple. Which is why it's so frustrating they rarely all work as they should for any length of time. I've pulled and wired and messed with a bunch of trailers over the years. I've yet to meet anyone who has messed with trailers for any appreciable amount of time who can say "I never have any issues with trailer lights/wiring" LMAO. As saddlesore pointed out, my frustration on this was the with the brakes, and specifically the plug on the truck.

And as a matter of fact the lights I've got on my 2 current trailers have 2 wires, neither of which is the ground. I almost upgraded to LED's (the ones I looked at did have 3 wires one of which was a ground) but didn't want to drop the coin.

You're right in that 12V wiring is as simple as wiring gets. The problem isn't with new stuff. The problem is gremlins in older stuff, especially stuff that doesn't have any loom around wires strung inside of small spaces, like a trailer frame. Is your grounding problem the ground wire, the connector, or has your wire worn through due to no loom and you're grounding inside of the trailer frame? Or a combination or all 3? Regarding brakes, the above grounding scenarios could be the issue, or your actuators could be faulty, or they could be rusted open, or shut. If you bought used, add in that lord only knows what sort of madness resided within the cranium of the trailer's previous owner.

not addressing the brake issue...

but on the wiring, all the rain we get every winter over here, just plays havoc with the lighting on my trailer...

So I went down to Platt Electric Supply and bought encased wiring in rubber, for about $60 for the trailer.... put in sealed lights...all the parts ran me right at $100....

but since I quit messing around with cheap crap from the Auto Parts store, and took the time to do it right, I've had zero issues over the last 3 winters now...

The summer when I was four, mom said I took a piece of metal that formerly connected the drive wheels on a wind-up choo choo, climbed up on a chair and with one hand on the exposed steam radiator pipe, inserted the thin metal piece into a wall outlet.

I'd already learned not to grab the radiator pipe in the wintertime when the heat was on, so that wasn't a factor.

Got lucky the first time and picked the "hot" slot, wound up under the kitchen table screamin' that my tummy was on fire. Mom was always too dramatic with her descriptions.

So naturally when I was all growed up, got into working in housing construction as a plumber and electrician, among other things. Ain't hardly been jolted since the episode in the kitchen.

As for trailer wiring, I have owned a trailer of some sort since I was 17 and now have two. In my (51 years) experience, trailer wiring only works when it really friggin' feels like working, regardless of anything done by me.

One year I hauled the double axle flatbed to hunting camp to fetch a coupla cords of firewood home. Lights/brakes worked find when I left home. Hooked 'er up for the trip back, only had brake lights/turn signals. No problem, almost made it home afore dark.

JMHO from years of having trailers. Most problems I have run into have been grounding issues.

Very true. That's why most of us who've had problems in the past recommend running ground wires from the plug to the lights, not grounding through the frame. Frame grounding seems like it would work fine but most grounding problems seem to show up there.
Even worse is grounding through the hitch ball. Those always seem to fail when things get dirty.