The latest episode of 'Jim is horrible at trailer wiring'.

JimintheNorth

Member
Mar 6, 2021
21
My trailer light cracked and popped off. It's 4.5 x 8.5. I thought I could easily replace it, so I looked that up and found a couple lights that fit. One has a reverse light:
Bargman Trailer Tail Light - 5 Function - Incandescent - Rectangle - White Base - Red/Clear Lens Bargman Trailer Lights 30-92-002 (etrailer.com)

upload_2021-6-21_11-25-59.png

It has two white wires, a green a red, and a black.

Another is just a tail light:

Bargman Trailer Tail Light - 4 Function - Incandescent - Rectangle - Black Base - Red Lens Bargman Trailer Lights 30-92-106 (etrailer.com)
upload_2021-6-21_11-27-12.png
One black, one green, one white.

However, when I look at my trailer wiring, it's DIFFERENT.

I have *two* white wires coming out, *two* green wires coming out, and a red wire (maybe for reverse lights?) terminating to nowhere. Where does the black go? If I go with the cheaper light how do I tie 5 wires into 3? How can I make sense of this to buy the correct light?

upload_2021-6-21_11-24-51.png
 

eoleson1

Super Active Member
Jul 5, 2011
3,636
Macomb County Michigan
It's kind of hard to tell based on your picture, but I think the white wires are ground, the red is brake/turn light, and the green is the tail/running lights. Here's my best guess:

White: comes from trailer, goes to light, goes back to trailer to feed the other side

Green: same as above

Red: comes from trailer, goes to light

So I think your five wires are only really three. The best way to tell would be to check it with a volt meter. Do you have one?
 

SteveP

Super Active Member
May 21, 2015
2,647
You'll need to run an extra wire from the center pin of your 7 pin connector for backup lights, assuming that the 7 pin on the TV side is already wired for trailer backup lights.
 

Raycfe

Waterford Ct.
Oct 3, 2007
18,435
Waterford, Ct
To be should you have to test each wire for function ....... you a test light or voltmeter. The whites are ground this is a given. Any wire that goes to another light should be the tail/marker light the remaining wire would be the turn/stop (trailer wires should be a different color from side to side).
The wires on the new light ............ usually the black is the tail/marker part of the bulb and the green turn/stop.
 

popup-flyer

Active Member
May 11, 2021
350
Central Texas
My trailer light cracked and popped off. It's 4.5 x 8.5. I thought I could easily replace it, so I looked that up and found a couple lights that fit. One has a reverse light:
Bargman Trailer Tail Light - 5 Function - Incandescent - Rectangle - White Base - Red/Clear Lens Bargman Trailer Lights 30-92-002 (etrailer.com)

View attachment 75961

It has two white wires, a green a red, and a black.

Another is just a tail light:

Bargman Trailer Tail Light - 4 Function - Incandescent - Rectangle - Black Base - Red Lens Bargman Trailer Lights 30-92-106 (etrailer.com)
View attachment 75962
One black, one green, one white.

However, when I look at my trailer wiring, it's DIFFERENT.

I have *two* white wires coming out, *two* green wires coming out, and a red wire (maybe for reverse lights?) terminating to nowhere. Where does the black go? If I go with the cheaper light how do I tie 5 wires into 3? How can I make sense of this to buy the correct light?

View attachment 75960

For the record, when wires are connected that is really just "one" wire. You said you have two white wires coming out. You have 1 white wire with a wire "tap" to connect another wire in. All 3 are still part of the same "leg" of the electric circuit.

As suggested the best thing to do is test. You can use a test light like this one:

https://www.amazon.com/dp/B08K79BFM...wg=kd1LW&ref_=sbx_be_s_sparkle_mcd_asin_0_img

or just one with a bulb the lights for 12VDC testing. Connect the long wire off the handle to the body of the trailer, turn on a signal light for turning or press brakes or even turn on parking lights and test each wire in each situation until you detect voltage by touching the metal point to a metal wire tap part or piercing the wire cover with the needle making contact with the wires inside. Then you know what its for.

For instance, if you have 12V DC present when the left blinker is flashing (for flashing this means the power will fluctuate from 0 to 12V it won't be 12V continuously so dont rush the test) that means you have found your left blinker power wire.
 
Last edited:

fredhead

Member
Jul 30, 2019
67
Norfolk. VA
On American trailers, for lighting, you would have four wires. Again, I'm only talking about lights. Each taillight would have either two bulbs or (more likely) a single bulb with two elements. One element burns brighter than the other. The dimmer element is your tail or running light. The brighter one is a combination brake and turn signal light. When you hit the brakes with a turn signal on, one light will burn constant while the other flashes. On a 4-Way flat trailer wiring harness, white is the ground, brown is running lights, yellow is left turn signal and green is right turn signal.
 

Snow

Super Active Member
Jul 19, 2007
12,272
Ontario
1st picture: Our original camping beagle.. would "sing" on cue when asked.. gone almost 3yrs but not forgotten.. (13 years, 3 months)

2nd picture: the mouthy sister.. she doesn't "sing" just barks.. for everything.. (10 yes okd)

3rd picture: the almost 3 year new "brother" he's still a pup at 5yrs.. and is the goofy one ..
 

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