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View Full Version : Trailer lights wiring help please


crousehouse4
03-08-2010, 04:50 PM
I'm trying to wire my trailer to the car so I bought one of the four wire connectors and this isn't working.

Here's what I've got...
from the trailer there are a total of four wires
-brown and yellow go to the right side light of the trailer
-brown and green go to the left side light of the trailer
(there is no white wire comming from the trailer, I looked under it...just the two wires going to each light)

from the car connector there are four wires...
-brown
-yellow
-green
-white


I tried connecting the two brown wires from the trailer to the one brown at the car, then green to green, and yellow to yellow... the nothing to the white. This didn't work.

Any ideas?

jsw2008
03-08-2010, 04:58 PM
I might not be understanding you correctly, but I think the white wire needs to be grounded to metal on the vehicle.

FourTrees
03-08-2010, 05:01 PM
I might not be understanding you correctly, but I think the white wire needs to be grounded to metal on the vehicle.

Exactly.

You are good on other colors.

There should be a white ground wire that runs to lights. Without it you have only a positive flow of power, and nothing to ground it to or in other words cause the "shock" to power the light.

If there is no ground wire on trailer you are missing something, and may have to get some ground wire to run on trailer.

crousehouse4
03-08-2010, 05:25 PM
That makes sense. The the thing is that when I bought the trailer the guy had it wired without a ground. SO, I assumed that I could wire it up the same way now. (The only reason I bought a new connector is that the other one came undone while I was driving and got messed up while dragging on the road.

I need to figure out where to ground it now.

Dave0013
03-08-2010, 05:37 PM
Yellow - right blinker/stop light
Green - left blinker/stop light
Brown - parking lights (one wire on the car to both trailer lights)
White - ground

But the guy who sold you the trailer was "correct" in his wiring. You don't necessarily have to have a wire ground because most light kits ground directly to the trailer. If you look inside of the light housing, you'll see that there is a metal spade which contacts the trailer when you tighten the bolts. Therefore, the ground between the car and trailer is complete when you connect the trailer hitch to the ball. So... if you are doing this work and do not have the trailer hitched to the car (i.e. the car is merely backed up the the trailer), it won't work without ground wires from both the trailer and car. I never bother grounding any of our trailers and all of the lights have always worked.

AI Inc
03-08-2010, 05:42 PM
Just ground the white to any bolt ( you want to clean it up first , get all rust out) anywhere on the tounge. I usualy use something on or around the stand.

crousehouse4
03-08-2010, 05:43 PM
Actually when I was trying it today I didn't have the trailer hitched to the car! I have to go try again...

Dave0013
03-08-2010, 05:45 PM
Actually when I was trying it today I didn't have the trailer hitched to the car! I have to go try again...

LOL. That's probably a more common mistake than you realize. Good luck!

crousehouse4
03-08-2010, 06:42 PM
Still didn't work. I had the lights connected before but not the trailer hitch to the car. I just tried them again with the hitch to the car and there is no change.

Richard Martin
03-08-2010, 07:27 PM
You should have a white ground on the trailer whether it's on the ball or not. Using the ball as a ground is what lazy people do. It can also cause the lights to flicker going down the road.

Probably what the other guy was doing was just using the turn lights and nothing else. If you run 12v in on a brown wire and then run it out on a green or yellow wire the lights will still light because they share a common ground inside the bulb. It's definitely not the right way to do it and can result in some bizarre light behaviors.

AI Inc
03-08-2010, 07:29 PM
Still didn't work. I had the lights connected before but not the trailer hitch to the car. I just tried them again with the hitch to the car and there is no change.

The trailer end that plugs into the truck will have a white wire about 2 ft long. Bolt that to a ground on the trailer.

ALC-GregH
03-08-2010, 08:11 PM
The trailer end that plugs into the truck will have a white wire about 2 ft long. Bolt that to a ground on the trailer.

then make sure the white wire on the vehicle is grounded to the chassis somewhere. Doing this will allow the lights to work without the coupler/ball connected. Even though I have no clue why the lights would need to work if the trailer is disconnected.

Also for future reference, green is right and yellow is left. Brown is park/running lights.

brucec32
03-08-2010, 09:25 PM
Trailer attached to the CAR? This thread really needs pics.

Larson Lawn Care
03-09-2010, 12:25 AM
Every year for the past 5 years I've had to replace the wires and/or lights on my trailer. I had no clue why the lights would stop working on me. I just bought the new LED lights with a wiring kit today and re-wired everything and replaced the lights. Only one light was working. So I took the light over to the other side (the side that was working) and checked to make sure I didn't get a defective light, and it worked. It took me a while but I figured out that it wasn't getting a good ground. So I cleaned the hole where the bolt goes and whata ya know it worked. Hopefully no more annual re-wiring... I'll check the ground first if anything goes wrong in the future. I also checked my fuses and the fuse for the light that didn't work was blown. It still didn't work after I replaced it until I found out it was the ground wire that was the problem. So my advice is to check the fuses and figure out the ground problem.

AI Inc
03-09-2010, 07:54 AM
Well Mr Larson ya still did the right thing. It takes about 10 min to run new wiring as opposed to possibly hrs fixing nicked wires. I run a new set every couple of yrs.

ALC-GregH
03-09-2010, 08:03 AM
common ground is the leading cause of faulty lights on trailers. ALWAYS make sure you have a good ground to the trailer and the light fixtures are grounded well too.

I worked at a U-Haul center for 13 years. They are the worst for getting lights to work as they use the hitch to ground the trailer. I can't even begin to tell you how many ground wires I had to run to trailers from vehicles just to get the lights to work. Then the hundreds of trailers I built from scratch and wired up.

ALC-GregH
03-09-2010, 08:26 AM
Correction, I worked at a "dealer" for 13 years. We were a authorized repair shop for U-Haul. I was the guy you'd see laying on his back under a U-Haul truck sitting on the side of the road in the rain with water running in my pants leg and out my armpit. Man I hated dealing with break downs. The only thing that kept me doing them was the pay. $35hr from the time I left my house to the time I got home. Most breakdowns were 3-4hrs each. 2-3 a week and I had another paycheck! :D

Ever try to replace a exhaust manifold on a 1990 E-350 with a big block 460 in it? If ever asked to do it, PASS. Biggest PITA ever.