how should trailer lights operate?

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  #1  
Old 12-01-09, 10:31 PM
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how should trailer lights operate?

I have a 2004 Dodge Dakota truck and the bed of a 1986 Nissan pickup as a trailer.

The tail lights on my Dodge behave as such:
o When headlights on, top part of tail light is lit.
o When braking, top part of tail light is lit brighter.
o When in reverse, bottom part of tail light is lit. At no other time is the bottom part lit.
o I assume this is normal behavior, as my wife's Hyundai Elantra behaves the same.

The tail lights on the Nissan trailer behave as such:
o When headlights on, top part of tail light is lit.
o When braking, bottom part of tail light is lit. At no other time is the bottom part lit.
o Forward or reverse made no difference in lighting.

Is this how trailer tail lights should behave? Is it possible for the 1986 Nissan to be wired this way, and newer vehicles wired differently?
 
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Old 12-02-09, 03:21 AM
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86 Nissan has separate signal and tail light assemblies. Back then, you had to order a converter to make regular trailer lights work. BUT, since you have one as a trailer, and you are getting all the functions, it would seem all is well.
Now, you say "upper" part. You didn't say whether it was orange or red, so clarify that so we can help further.
 
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Old 12-02-09, 12:09 PM
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The upper part has a red cover, and the lower part has a white cover.
 
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Old 12-02-09, 12:29 PM
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The Nissan is probably using single filament bulbs, one for each bay and one for each function. You can probably get it all to work in the upper bay by rewiring the two hot wires (one tail light and one brake/signal) to a double contact receptacle. Then snap it in the upper bay and leave the bottom bay alone, since it doesn't matter about back up lights on a trailer.
 
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Old 12-02-09, 02:46 PM
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Originally Posted by soy8g4 View Post
o When braking, bottom part of tail light is lit. At no other time is the bottom part lit.
You forgot the directionals.

I recently learned myself, in a thread I started (by Ecman51`) regarding trailer lights, and learned how the same wire operates the directionals. You never mentioned the directionals. They probably flash through the brake light filament. I am guessing trailer lights are possibly done in a universal method with 4 wires and 4 prong jacks? Wirepuller is the one who gave me my answer there in Automotive.
 
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Old 12-02-09, 10:05 PM
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Left and right turn blink correctly on upper part of tail light on both my Dakota and the Nissan trailer.
 
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Old 12-05-09, 04:18 PM
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Any idea where I can find the wiring diagram of a 1986 Nissan 720 truck tail light? I removed the electrical tape around the wires, and found one tail light wiring to be 4 wire, and the other went from 4 wires to 9, and both tie into a 4 prong connector. I have no clue what the person who wired this was thinking. I suppose I could go trial and error to figure out each wire, which can't be hard since there are only 4 wires.
 
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Old 12-06-09, 12:02 AM
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I unwrapped the wires and discovered the following connections of Nissan tail light to Phillips 6-way towing adapter:
Nissan tail light has green, yellow, black, and red wires.
Green connected to green (right turn)
Yellow connected to yellow (left turn)
Black mapped to white (ground)
Red mapped to brown (tail light)

However, the person who wired it had the black coming off the Phillips 6-way adapter split to 3 wires, one of them not connected to anything, the yellow of one tail light connected to the yellow of the other tail light, with a wire in the middle connected to the 6-way's yellow, green connected to green of 6-way, and some other weird stuff.

I would think that the 4 wires I have now (brown, white, yellow, green) should have white connected to black of both tail lights so that each has ground, brown connected to red of both tail lights so that each has tail light, yellow connected to yellow of 1 tail light, and green connected to green of 1 tail light. There's no reason I can think of to have green and yellow going to both tail lights, considering left and right turn signal should only display on 1 tail light.
 
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Old 12-06-09, 01:52 PM
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Contact these guys, who responded to me on this thread:

http://forum.doityourself.com/automo...functions.html
 
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Old 12-07-09, 06:51 PM
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I figured out that the turn signal wire also acts as the brake wire. What I can't figure out is how the bottom part of the light, which is white, lights up at a valid time. The trailer light's black wire is ground, green is turn signal, red is brake, and yellow makes the bottom white light turn on. The problem is how to make it light up at an appropriate time, which I define as the same as my truck -- when gear is in reverse. Maybe the fact that the tail light is from a Nissan 720 truck but it's connected to a trailer 4-wire explains it; I'm going from my truck hitch's 6-wire to 4-wire, does "vehicle is in reverse" gets lost?

When it comes down to it, a regular trailer light (not a vehicle bed being used as a trailer) only has 1 light, not 2 that is typical on a vehicle. I'm leaving the yellow wire unconnected, and I'll have my brake/headlight/turn signal functionality.

I rewired it all last night and tested it out tonight, and all is well. Now to put the final touches on the wiring, then reinstall it tomorrow night, and I'm done. It has certainly been a learning experience, and one that takes patience and trial/error to figure out the wire mapping as opposed to relying on documents to be accurate.
 
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