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Trailer lights wiring question updated, dope slap coming

o.k. I did that. The black wire goes to a red light. The red light goes to a red light. They both work perfectly.

I need to know which one is brake/running and which one is turn signal.

on a old time light bulb I could tell from the filament, but no can do with LED. I can hook them up to the truck and test for function, but the goal here is to avoid standing around in freezing weather, connecting and unconnecting wires.
Its extremely cold, I totally get it. You don't have a small 12 volt?
 
Google is your friend, the red wire is the turn signal, the black wire is the brake lights.

P.S. This is a utility trailer with a fold up tail gate, and I'm going to put at least a running light on the bottom of the tailgate, probably a brake
light.


https://www.etrailer.com/question-8813.html


Editorial note: I have a set of submersible LED lights for my boat trailer, sitting in front of me, and the wire colors match those of the harness.

One difference is that the boat trailer lights includes a tag light for the left light so they are not interchangeable, the set I am putting on the utility trailer are the same, no tag light, you just flip the housing over to install the light.
 
o.k. I did that. The black wire goes to a red light. The red light goes to a red light. They both work perfectly.

I need to know which one is brake/running and which one is turn signal.

on a old time light bulb I could tell from the filament, but no can do with LED. I can hook them up to the truck and test for function, but the goal here is to avoid standing around in freezing weather, connecting and unconnecting wires.
You can put 8 double A batteries in series, or any 1.5 volt batteries
 
Any battery from a cordless drill will also work.
My nephew used to install all the strobe lights on the HERO trucks and they used a 18 volt battery from a cordless drill to test and program each light as it was installed .
 
Connect harness to vehicle. Use multimeter in vdc. Turn on lights. The wire with 12v should be running lights. Then turn off lights, turn on blinkers and find wire with 12v bursts.
 
So I read it one the internet, so it must be true. :tongue:

Thanks for all the help, I got it figured out.

Take about 3 minutes, and read these two answers by experts- same question - what does the black wire do and what does the red wire do on a set of trailer lights.

Both experts work for the same online company, the products from which are pretty good.

Post 15, Gaffer1968 Gaffer1968 posts this link. Wire Color Functions of Trailer Taillight that Use Red, White and Black Wires | etrailer.com

Post 12, I post this link,

https://www.etrailer.com/question-8813.html

Now take about 3 minutes, read both of these posts, and based on these posts, tell me what light on the wiring harness does the red wire on the new tailight hook up to? :pop2:

Remember, you read it on the internet.
 
So after flogging the interweb, and getting conflicting advise (see previous post) I tested the two light with my truck battery, and very methodically marked them R and L and Turn/brake and Run,

Then I looked a little more carefully, and the each light had a plug with three post that plugged into the back of the light (which I learned really facilitates installation as these are recessed lights)

AND IF YOU TAKE OFF THE PLUG, NEST TO PLUG ON THE HOUSING AND MOLDED INTO THE PLASTIC ARE THESE THREE WORDS - "GROUND, TURN, RUNNING" - :doh:
 
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