Trailer wiring question

[MikeA57]

My suggestion... Connect the black wire to your marker circuit and forget about the red wire. Problem solved. You have a clearance marker light on the back and you don't have to worry about isolating the turn signals from each other.

DING, DING, DING, DING!!! We have a WINNA!!!! That's what I got to thinking yesterday afternoon. To heck with the Red wire, this just overly complicates things and just having it as a tail light will work fine. I don't have the light bar attached to the trailer yet, just grounded, so I may try hooking the connector up to the truck and probing around with a small jumper and see what I can scare up on there. It would be an interesting experiment and I may even get my 13 yr old's brain thinking in another direction than 4 wheelers and girls....

NAAAHHHHH, that'd never work! :confused2::confused2:

 

[Smallplot]

Well, don't have to be 13 to think about 4 wheelers and girls do we? :laughing:

If you purchased it to use as a marker light, just hook it up that way. Just need to make sure if one of the wires is actually a ground. We just rewired our trailer about a month ago. I did change one thing, I grounded the brakes through my wiring, back to my truck. Had issues over the years of loosing ground (and brakes) when brakes were grounded directly to the trailer frame. Funny how sticks and grass can pull on dangling wires. And yes most lights are grounded through the bolts which attach to the trailer.

 

[Iplayfarmer]

... I may even get my 13 yr old's brain thinking in another direction than 4 wheelers and girls....

You may get him thinking in an additional direction, but you won't replace the 4 wheelers and girls.

 

[Iplayfarmer]

...yes most lights are grounded through the bolts which attach to the trailer.

I haven't see it all, but I've found that most LED lights include a separate ground wire (white). The regular filament type lights are grounded through the mounting bolts.

 

[Smallplot]

I haven't see it all, but I've found that most LED lights include a separate ground wire (white). The regular filament type lights are grounded through the mounting bolts.

You are correct, my apologies. I forgot they we LEDs.

Poor folk like us don't have fancy stuff like lights an all. We just wave cause everyone around here know where we go'in.

 

[Iplayfarmer]

...Poor folk like us don't have fancy stuff like lights an all. We just wave cause everyone around here know where we go'in.

... but have you ever heard directions like "take the second right before where the old Hanson's barn used to be."

Actually trailer lights are a bit of a fascination for me. As a kid we always borrowed trailers and never had the right hook ups for the lights. Now that I have my own trailers it seems like the ultimate luxury to drive at night and not feel worried.

 

[Smallplot]

... but have you ever heard directions like "take the second right before where the old Hanson's barn used to be."

Sure. They usually just say take the road at Hanson's even though a Hanson has not owned the property for 40 years. And the barn burnt because the bucket brigade did not get there in time. Lol.

 

[crbr]

Good reading......

 

[Iplayfarmer]

I must admit that I have found myself slowing down for a large outfit in front of me even if they aren't signaling just because I know the outfit, and I know the owner's farm yard is coming up in a few hundred yards.

 

[boggen]

I must admit that I have found myself slowing down for a large outfit in front of me even if they aren't signaling just because I know the outfit, and I know the owner's farm yard is coming up in a few hundred yards.

i generally pull over to other side of lane some. to keep folks from passing. as well.

been way to many hot rods. thinking they can pass me and tractor or trailer ahead of me in one pass. with near misses.

 

[MikeA57]

Well, the first attempt at a hookup didn't work. But then, I did just take the pigtail I bought at TSC and wired it up color to color. Right turn signal worked the left trailer light and on the rear LED bar, no running lights on the right side and Left turn signal didn't do anything. So I checked continuity between the terminals at the junction box and at the connector of the cable that hooks up to the vehicle. Their pin layout was way off compared to what GMC's is. I didn't have time to remake the connections last night due to a kid's football game but I'll jump on it tonight and see if I can't get things running right. At least now I know what colors of the pigtail need to be connected to which color of the trailer light wiring.

 

[Iplayfarmer]

Well, the first attempt at a hookup didn't work. But then, I did just take the pigtail I bought at TSC and wired it up color to color. Right turn signal worked the left trailer light and on the rear LED bar, no running lights on the right side and Left turn signal didn't do anything. So I checked continuity between the terminals at the junction box and at the connector of the cable that hooks up to the vehicle. Their pin layout was way off compared to what GMC's is. I didn't have time to remake the connections last night due to a kid's football game but I'll jump on it tonight and see if I can't get things running right. At least now I know what colors of the pigtail need to be connected to which color of the trailer light wiring.

If you have brakes, watch the location of the brake vs. auxilliary on the GM vehicles. Any adapter or harness I've ever gotten has the auxilliary power from my Chevy going to the brakes of my trailer. This doesn't work well for pulling. :laughing:

 

[MikeA57]

Thanks IPlay. Yeah, I had to move the yellow, green, and brown around in the junction box but I got them to work.

Now it's just matter of adjusting the brakes and putting the boards by on. I've put 2 heavy coats of diesel/oil mix on the edges and the bottom sides of the boards and tried saturating the ends as best I can with it too. Once I get them back on the trailer I'll coat the top side of the boards.

Oh yeah, I also picked up some of that 1 1/4" wide camper tape that's used on pickup truck beds to insulate and cushion a pickup topper and I laid that down all the cross members and down the edges of the trailer. Trying to keep the pressure treated wood off the metal and maybe quiet down the trailer some too.

And while we're talking about this, I've got another question:
When they were setting up the standard on these round 7 pin plugs, why didn't they make the center conductor the GROUND connection? It's the largest one of the bunch and it just seems that making the center pin ground then all the other light/brake connections surrounding it would make the most logical sense. It's almost like it was an after thought to even use the center pin. ("Oh wow, somebody wants to hook up their backup lights. Well let's just use the center pin, it's not being used for anything!")

 

[Iplayfarmer]

... It's almost like it was an after thought to even use the center pin. ("Oh wow, somebody wants to hook up their backup lights. Well let's just use the center pin, it's not being used for anything!")

I've thought that too. I don't have any answer for why the system is set up how it is. The only part of the 7 pin connection that makes sense to me is that the left turn signal is the left most pin, and the right turn signal is the right most pin.

 

[MikeA57]

Well it is on the truck, but not on the plug I bought!!

EDIT:
Let me rephrase that. The left/right turn signal connectors are on the left & right side of the plug, but it's the WIRE COLORS that are different from "normal" trailer wiring. I found an illustration of the pin out of the plug that I bought. Now, that's the 'standard' for the RV industry but I wasn't even aware of that until just a day or two ago. I was still thinking in 4 wire trailer layout.

And they used White, Yellow, Brown & Green wires in the 7 pin connector but they assigned different uses to them. WHY?!?!? Could they not have carried over those colors to the same use in the 7 pin that they had in the 4 pin??? Why cause seemingly unnecessary angst by changing what purpose the wire colors had?

There's always got to be somebody fiddlin' with stuff.

And mark my words, somewhere in that whole mess there was an engineer involved in it. I just know it!!!!

End Edit, End Rant --

 

[boggen]

*laughs hard*

i be remembering going through same stuff you doing now. of different colors.

i just plain gave up on color coding scheme. and got some tape and a marker. and a dc volt meter (10 bucks local hardware store), and checked what was what. and went at it from there.

i have had grounding problems with trailers in the past, so i just run ground wire to all lights, even if it means just striping the plastic back and placing it behind the screw / bolt that holds the light on.

==========================
for folks that live in cities were theft is high. i tend to see folks going with like a key lock pins, key locked chains, key locked hitch, etc...

but i have read folks, completely re-arrange the wiring on both the vehicle and trailer on purpose. so if trailer is stolen, and the thefts use regular hook up connector on there vehicle, a chance that a cop might see, someone trying to turn left, but the trailer lights are blinking to turn right. or some such. but when hooked up to your vehicle it works like it should.

 

[rasimmo]

You guys are expecting too much. You want someone to design a system that makes sense. What are yall thinking?:laughing:

Back to the light. I have a light like that on the top rear of my horse trailer. turn signal and brake
I am not sure how it is wired or how it is hooked up, never had a need to remove it. I just know that it is possible. Whether you have that type of light or not I do not know.

 

[Iplayfarmer]

I'm resurrecting this thread because I've spent a lot of time considering the original question... How do you hook up a center light to come on only when the brake is applied? I know Mike got his trailer wired and working satisfactorily, but it's bothered me that we never really came up with a good way to do this.

I had a brainstorm the other day as I was following a truck pulling a trailer that had a separate brake light top center. Use a 12V relay that pulls a very low amperage signal from the electric brakes. The power for the lights could come from an auxilliary terminal or from both signal lights with diodes in the right places.

Sorry if someone already proposed this and I missed it. Let me know if there's a reason why this wouldn't work.

 

[Iplayfarmer]

Ureka!! I've found the official answer...

Vehicle to Vehicle Taillight Converter Tow Ready Tow Bars 118158

Thanks to Soundguy for mentioning it on another thread.