Pickup bed trailer tail lights questions

Malamute

Malamute

Adventurist
I made a trailer out of my old 89 Nissan pickup. It didnt have enough wires in the harness in the middle of the truck to make all the correct brake lights come on, it makes the amber turn signal lights go as brake lights (they also work OK as turn signal lights) and I cant find any wires in the main harness that make the other red high output brake lights work. Is there a way to make the actual brake lights on the Nissan work?

Do I have to follow the wires from the tail lights in the back forward to where they do whatever magic makes them work? I dont think I have much from the large round trailer plug that would make the brake lights work independently from the turns.

Edit: Forgot the mention, the trailer has a small flat squarish device in the wiring between the factory wiring harness it was tapped from and the trailer plug in the rear bumper of the old pickup, can I take power from that to my brake lights? Is the little square device the magic part that unscrambles the brakes from the turns?
 
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Does anyone have a wiring diagram for an 05 4runner? Specifically the tail lights color codes, the stop lamps in particular.

Not sure exactly how the trailer plug is wired, but I think I'm going to tap the tow vehicles stop lamp circuit and use it for the trailer stop lamps. Its set up so the plain trailer lights work as stop and turns, which would seem OK if only using the plain combination trailer lights. Havent figured out how to separate them, the ambers on the trailer come on with the brakes. :(
 
Oooo You're getting into a very touchy situation here.

The boxes found in the back end of all vehicles with a trailer plug on them are relay/diode boxes. They protect the vehicle from feedback from trailers.

Vehicles have more complex lighting than trailers, both simplified and not in any particular order;

1 Stop Lights Left/Right
2 Running Lights Left/Right
3 Left Turn signal
4 Right Turn Signal
5 Backup Lights
6 Ground

Four Pin Trailer plugs have;
1 Running Lights Left/Right (plus side running lights)
2 Left Brake Light AND Left Turn
3 Right Brake Light AND Right Turn
4 Ground

The little black boxes combine the brake lights and turn signals into one output, so that when the left turn signal is applied, it sends power to the left brake light on the trailer.

Typical trailers do not have amber turn signals and some don't have backup lights. Even a 7 pin connector wouldn't solve that problem.

If it were me, I would scrap the factory wiring, and run a new 7 pin or 4 pin trailer harness, and connect my new harness accordingly at the trailer lights, skipping the lights I don't have wires for in my new harness.
 
Its a 7 ̶p̶i̶n̶ blade There is actually enough pins to run backup lights, and a separate brake light circuit, but its also the one used for trailer brakes. I dont have brakes at this point (may at some point), so am going to use that pin for the brake lights. Trying to figure out how to disconnect the brake and turns so they work independently. I may need to have optional wiring for different setups. My cargo box was OK with the combined brake and turns. Perhaps I should use a 4 pole flat plug for it thats run through the adapter, and wire the 7 pole so its the way I need for the trailer.

The plug on the tow vehicle seems to be wired in basic 7 ̶p̶o̶l̶e̶ blade RV setup with the exception of the brake/turns being combined. Theres nothing hooked to the aux power from the tow vehicle that I can tell. I havent crawled under it yet, I have some back problems that make that difficult, with long lasting effects.

This is what I found that corresponds to the way its wired (couldnt find the card that came with the plug that gave me the color codes for the plug) When I hooked up the backup lights in the trailer plug, they worked, the tow vehicle was already wired for it. Nothing is wired into the trailer bakes at the moment, I'm thinking of tapping a brake light wire in the tow vehicle for the brake lights in the trailer, if I can just get the turn/brake apart. I guess if it has the adapter module I can bypass/remove it?

http://www.hopkinstowingsolutions.com/support/wiring-guides.html
 
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The last thing you want to do is modify, or even ATTEMPT to change what the pins do on the vehicle side of the plug. Remember that part I mentioned about protecting the vehicle side from the trailer? It exists for a reason.

Follow the 7 pin layout that you can find on google images or a plethora of other places around the internet, and stick to it. Don't try to be creative.
 
OK, that makes sense.

I edited my previous post when you were writing I think. Is there a relatively innocuous way to make the trailer brake lights separate from the turns without making a possible problem later if undetected and used with a standard trailer? The trailer brake pin seemed the simplest to use for trailer brake lights. Perhaps not.
 
No, because the signal from the turn signal and the brake lights are combined within your towing vehicle in the trailer plug module. After that, there is no way of separating them. Modifying this, not only do you destroy system protection, but you ruin your vehicle from towing literally every other trailer in the world.
 
So, it looks like I should skip the ambers, and separate the brake circuits in the pickup trailer tail lights and use them as turns/brakes like common trailers. Think clipping the brake wires so they are separate and running the amber circuits to the individual brake lights on each side should work. Does that make sense?

That would use common plug functions, just bypassing the ambers and separating the brake lights for individual sides in the back of the trailer.


And thanks!
 
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The solution ended up being fairly simple. I had all the connections to the plug from the old truck wiring made when trying the ambers. I ended up removing the spade from the ambers and put the spade for the red brake lights in the place where the amber spades used to be in the tail light connectors, clipped the connector back up, and it works fine with the red stop lamps being turns and brakes. A horseshoe nail was perfect for reaching into the connector and releasing the plastic clip that held the spades into the connector. Need to leave one in my tools now.
 
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