Electric trailer brake ghosts

[Daren Todd]

So, I got a piece of equipment in today. Trailer lights and wiring were messed with pretty good. Electric brakes were unhooked. 7 prong trailer light connector was missing, and a 4 flat was installed. So, I had to bring it back up to DOT specs.



Ran new wires for the brakes. Hooked the lights back up. Replaced one of the lights. Other light looked good. Hooked the 7 prong trailer light connector up. And went to testing.



This is where the WTF???? Started



Hooked my ranger trailer light tester up. Checked parking lights, and heard the brakes kick on checked brake lights. With the same results



Now the brake wiring is completely seperate from the light wiring. Hence the WTF moment.



Disconnected the trailer brake wire from the 7 prong connector. It's still engaging the brakes when power gets put to the lights. Checked the prong on the 7 pin for the electric brakes. No juice going to it. Checked with meter and test light. Hooked up test light to power wire for the electric brakes. And was getting power. But.... the only thing hooked up for the brakes is the ground.



Cut the ground wires going to the new trailer light. Brakes released Guess I have some lights to rewire as well

 

[Daren Todd]

Well, the solution ended up being foolish and simple. Was getting a back feed from power through the ground and was engaging the brakes. Found a mess in the wires going to the trailer lights. So I rewired the trailer lights, and ran a seperate ground to the lights themselves.

Grounded the brakes to the frame. And cured the issue

 

[D2Cat]

Daren, I admire anyone who can solve brake wiring problems!

I just got done, I thought, with wiring my GN stock trailer. Rewired everything, but use the existing lights. Installed a junction box on the trailer to clean up the previous mess and simplify things for me.

Everything is working as it should except the left brake light is on all the time.

I need to wait until cooler weather and maybe my thinking will be clearer!

 

[Hassman]

I was chasing my tail the other week with a 7P trailer connector as well -I had bought a trailer and they sent with the 7P socket for me to install on my truck.
Turns out Nissan runs 2 different grounds -that messed me up good and proper; tail lights and back-up lights run off of 1 ground and the indicators and brake lights run off another.

Once I had finally figured that out I connected the trailer -no tail lights, no brake lights.?.? Not the same ground so what the heck??
Then remembered that I do not trust anyone else for a reason, so opened up the 7P on the trailer -instead of stripping the ends of the wires they had just put the wires in hoping that the screw would bite into the conductors... well some of them worked...

I learned (again) never to trust anyone else's electric works.

 

[Daren Todd]

Daren, I admire anyone who can solve brake wiring problems!

I just got done, I thought, with wiring my GN stock trailer. Rewired everything, but use the existing lights. Installed a junction box on the trailer to clean up the previous mess and simplify things for me.

Everything is working as it should except the left brake light is on all the time.

I need to wait until cooler weather and maybe my thinking will be clearer!

Here's a couple things to check. Had a similar issue with my service truck. When I test the lights with my test box, they all checked out. But when I hooked it to the truck, my left turn signal would stay on all the time. Come to find out, the plug in on the trailer had a couple spades that were smaller. It would cause the pin on the connector on the truck to press into the another pin Swapped out the 7 spade on the trailer and had no more issues.

You may have accidently crossed your aux power and the turn signal when you did the junction. Or the third option.

Did you replace the 7 pin connector on the trailer with one labeled for color instead of the use for the terminal?

Reason I bring that up, is half the 7 pin connectors that are labeled for color coding are non standard. So, I'm thinking your left turn signal and aux power could be swapped. If that's the case. I would be willing to bet also, the tail lights and brake light are swapped on your right turn signal as well.

I had a tractor trailer load of DOT compliant units shipped in, where I had to wire up the lights, brakes, mount the axles and tongues on them.

Well the first one I did, I backed my truck over and hooked it up. Had the same issue

Took a couple hours tracing wires before I got it figured out.

Brown was the right turn signal, instead of tail lights.

Green was parking lights.

Yellow was aux power (charges the battery)

Red was left turn signal/ brake

Black went to back up lights.

White was ground.

Blue is the electric brakes.

Most trailer lights have yellow/brown for left turn, and green/brown for the right side.

Brown is parking lights, green is right turn, and yellow is left turn at the lights

 

[Tooljunkie]

I need to pay attention to diagram, occasionally i find myself mirroring the connectors. Wired connector as viewed from other side. Also paying Attention tolocating pin in housing.

Done it enough i should have it figured out by now.
U.S industry standard is different than Canuckian standard. At least it used to be.

Had a customer use a hoppy adapter, brakes would pulse when left signal was avtivated. Simple change. Had to swap a couple wires.

 

[Daren Todd]

The only ones that are standard here are the four flats bought five 7 prongs a while back. Just grabbed the $9.99 ones off the rack. 3 were the same and marked with abriviations by the terminals.

Then got 2 that were marked colors. They were opposite each other one used the same colors as a 4 flat for the lights. The other was bass ackwards. Had to swap the yellow and red, and the green and brown

 

[D2Cat]

Well, in my comatose state I had a couple of wire tied in wrong.

I took the plug apart and sketched out the location of each pin and the color of wire attached. Then went to the junction box and made sure the grounds were all correct, and the blue was correct, making brakes OK. Then as I went through the junction box I had a couple of lugs on the wrong terminal... one of them being the power to the yellow! So I had power all the time. Since I don't need that power wire, at least not now, I put on an extra lug just to keep it out of the way.

I dropped the little set screw the holds the 7pin end in the housing, and it was in a rock drive. Had to go get a magnet to find it. But I found it and all lights are now working properly.

Thanks, you got me motivated!!

 

[Wild and Free]

I have bought and sold many trailers over the years and find it truly amazing how many different ways people can find to screw up simple trailer wiring and brake wiring so bad. I find it comical.

My latest venture was a PJ dump trailer, I had never seen such a messed up plate of spaghetti for wiring inside the pump box, took me about 4 hours just figuring out what went to what and eliminated duplicate wires then reroute and clean things up so one could actually see how it was supposed to work.

 

[Daren Todd]

Well, in my comatose state I had a couple of wire tied in wrong.

I took the plug apart and sketched out the location of each pin and the color of wire attached. Then went to the junction box and made sure the grounds were all correct, and the blue was correct, making brakes OK. Then as I went through the junction box I had a couple of lugs on the wrong terminal... one of them being the power to the yellow! So I had power all the time. Since I don't need that power wire, at least not now, I put on an extra lug just to keep it out of the way.

I dropped the little set screw the holds the 7pin end in the housing, and it was in a rock drive. Had to go get a magnet to find it. But I found it and all lights are now working properly.

Thanks, you got me motivated!!

Your welcome buddy I've lost count the of how many times I've lost those bloody set screws Usually they end up in the expansion joint in the shop floors Got to the point, I took one of those screws to home depot and bought a box of 50 but then, I'm rewiring and swapping those plugs at least 2 or 3 times a week Sometimes with a customer standing over my shoulder chomping at the bit to get on the road

 

[Daren Todd]

I have bought and sold many trailers over the years and find it truly amazing how many different ways people can find to screw up simple trailer wiring and brake wiring so bad. I find it comical.

My latest venture was a PJ dump trailer, I had never seen such a messed up plate of spaghetti for wiring inside the pump box, took me about 4 hours just figuring out what went to what and eliminated duplicate wires then reroute and clean things up so one could actually see how it was supposed to work.

It amazes me at how complicated someone can make out of something that is pretty simple setup

I'm assuming a main power and ground going to the motor. With a rocker switch to tell it which direction to go, similar to a winch?

 

[Tooljunkie]

What used to get my goat was at the place i worked. Connectors ground off,torn off or crushed. Running wire through pintle ring and then plugging in. Keep in mind, most of these people are educated and members of law enforcement. High paying jobs with no practical skills.

The little set screw usually doesent need to be removed, but not all connectors are created equal.
7 wire metal connectors, although well made will cause abs faults when dirty and wet. Especiall in winter. That was a real head scratcher.

 

[D2Cat]

Frank, this 7 wire connector was made in Outer Mongolia!

I should have bought a new connector and the wire from it to the box. This connector had a set screw that pushed on a "U" piece of metal to anchor the wires, but it had a very small set screw to anchor the piece the wires anchored to. That screw was required to keep that piece for pulling out of the housing when removing the plug from the truck.

The wire that was used was nice and flexible and heavy gauge, but the colors were odd. It had no white wire, but a black. So that tells me it probably wasn't specifically for trailer hook ups.

When it comes to wiring and painting....I'd rather take a beating!!!

 

[Daren Todd]

If you work on trailer lights and brakes all the time, then one of these test boxes is a real time saver

The box does the 7 pins. I got a adapter with it that does the 4 and 5 flats, and the 6 round.

It makes trouble shooting a breeze. And if you have odd ball wiring, you can hook the plug to the box, and meter what color does what. With out having a second person inside the cab of a vehicle

Sent from my iPhone using Tapatalk

 

[Wild and Free]

It amazes me at how complicated someone can make out of something that is pretty simple setup

I'm assuming a main power and ground going to the motor. With a rocker switch to tell it which direction to go, similar to a winch?

Its got more to it than that since its a two way cylinder there are 2 solenoids for the pump motor and valves, both solenoids have to open and close valves for both up and down operation.
Then add in the on board trickle charger for the battery and then the hard wired control cable with a tee in it for the remote operation receiver. That is all in the pump box, the light and trailer box is all together a separate entity.

 

[Tooljunkie]

Yes, throw a hydraulic system and aux battery into the mix and then maintain charge on said battery and it tests your patience. So connect trailer and away you go. Drag it 160 kilometers on rough gravel and heaven forbid driver uses a little common sense and slows down some. Torn off wiring, cap gone off hydraulic resevoir and battery cracked and leaked all over in storage compartment.
And hes complaining that he had to unload garbage by hand.

I had to fix that mess.

 

[sheepfarmer]

Well I am always surprised and grateful if the lights etc work on my horse trailer. I think equipment that isn't used daily lies around and thinks of ways to not work. I used always to carry a can of contact cleaner in the truck, tooth picks to jam in the socket if the lightbulb wqsn't making good contact, and before panicking (and before loading the horses) drive it a bit. My old trailer was grounded to the truck via the hitch, or so I was told, and if the ball or the receptacle was rusty it made a lousy ground. My new one seems to be better. New meaning 2003 as opposed to 1979 .

 

[Tooljunkie]

Actually, the ground is carred through your trailer connector. You will find a white wire fastened to trailer frame (usually).

Depending on a trailer coupler for a good ground isnt the best in any case. My reciever is so rusty it would never carry any current.

A weak ground will also bring out the ghosts in electric trailer brakes.

Along with contact cleaner, a light coating of terminal grease will help also. I grease light bulb sockets too.

I built a trailer light tester at my last place of work, very handy when wiring trailers in winter, as shop was too small for truck and trailer. And working with door open at -30 sucks. Thats 60 degrees colder than it was today. Celcius.

 

[Daren Todd]

Actually TJ, on the older trailers, they didn't usually hook the ground wire up on trailer side of the plug. U haul was pretty bad about that on there trailers. Back in the early 90's my mom rented a trailer from them, and had them hook a ball to the bumper of my truck. Guy didn't tighten the ball up. Was just finger tight. Course I was in my early 20's and didn't know any better. Trailer lights were iffy when I left there lot. By the time I got to my parents place with the trailer, the lights were flickering on and off.

My step dad started checking everything over and found the trailer ball loose. Tightened the ball, and the lights worked great That's also when I learned a valuable lesson. Never assume someone installed the trailer ball properly

Fast forward to about 6 years ago. My step brother needed help moving and rented a trailer from u haul. My dad's truck wouldn't pull the trailer loaded, so I went down and hauled it for them. They still weren't hooking the ground wire up on the trailer plug