So I nabbed another deal from work; a Reese hitch along with a wiring harness, since apparently the previous owner of my truck never had a need for a hitch





Got the hitch itself installed; that was fun There's always ONE HOLE that doesn't want to line up properly... Nothing a big hammer didn't fix though










Topped off the install with a useless add-on for this truck, lol






Also nabbed a matching spare the same day, and that fit snugly into place





It's a little wider, but the overall height seems about the same, and that's what I was mostly concerned about.








But anywho, onto the main point of this thread. I've hooked up a few trailer wiring harnesses in the past, most of them just being the universal ones where you actually have to splice into the factory wiring on the truck. Those are simple; splice into the harness, attach the external ground, and presto you're done. I've done a few of the "T" connector type ones too that have OEM style plugs on them, the go between the factory wiring harness on the truck and the tail lights, and get the power that way. Those often have an external ground too.

This particular harness has me a little perplexed... It has a wire that I have NO IDEA what it's for It's a "T" style harness that goes in between the factory harness on the truck and the tail lamps, and it has an external ground, but then it's also got this extra wire with an OEM looking plug on it.











It's a fairly heavy gauge wire, and is just a single wire lead, but I have no clue what it's suppose to go to. To add to that, it's apparently crucial to the working of the trailer lights, because with it not hooked to anything like it is now, and the other wire grounded, there's no power getting to the trailer wire plug. The tail lights still work fine, so it's not like this is an emergency, but I'll need to get it figured out before I ever go to tow a trailer

To make matters worse, I have no clue who makes the harness either! There's no markings on the box or anything. It appears that it use to have some sort of identification sticker on the back of it, but it's long since been illegible... Could be a Reese adapter, could be factory, I have no clue.








Any ideas fellas?

 

4,6 or 7 pin plug? is it a 'factory' wiring harness, if so it should be a 7 pin.
Might try the FSM link or etrailer.com has some good trailer wiring diagrams.
If I still had my '05 I could check.

Edit-sorry-on my phone just noticed you don't know who made...

 

yeah I can't seem to find a converter online anywhere that shows with this extra wire

it's just the standard 4-pin output on it. the truck doesn't have the towing package, so I'm not even going to worry about hooking up a 7-pin, as I don't plan on hauling anything heavy enough to require trailer brakes anyway


I'm beginning to think that maybe it's a 12v + input; maybe this converter box acts more or less like a switch board instead of using power directly from the factory wiring. it pulls directly off the battery and then just picks up the signal from the running lights, brake lights, and turn signals, and the box then sends power to the trailer plug accordingly. maybe that's why the wire is so thick?

but then at the same time, the wire is black; I would expect a 12v + wire to be ANY color but black, lol, but who knows


if I can't find anything by the weekend, I'll have to walk out and look at the truck it was pulled from. I think they took the bed off it, so hopefully the wiring is still intact

 

it is wierd but it almost looks like the plug off the license plate light...wonder if it draws power from one of the two...

 

nah the license light plug has two wires and is more oval shaped, unlike this one which is just round

 

Well from what I can find, it's pretty much just what I thought it was as far as the way it works, and it's known as a "powered converter". It's its own dedicated circuit that gets it's power directly from the battery and sends that to the trailer plug whenever the input from the tail lights tell it to do so. SO, I think tomorrow I'm going to either see if there's a power wire ran back there somewhere for the towing package option (didn't see one today, but I didn't look very hard either), and if there's not I'll run a power wire up to the battery, put maybe a 20a fuse in line, and see how that works. What's the worse that could happen

It's very strange though how the plug just looks so factory. It would be awesome if Toyota has a wire already ran back there for the tow package, just nothing hooked to it and all I have to do is pop a fuse and/or a relay in under the hood! I need to go flip through the FSM really quick

 

well there was certainly no wire ran to the back if the truck didn't come with the tow package... no worries, ran my own

tapped into 12v inside the fuse box with a 30a fuse, then ran a wire all the way back following the factory harness through the cab, then down along the frame rail. which is easy until you get to about where the gas tank is... total PITA there... but otherwise it's simple. cut the plug off the trailer converter and used some disconnects for the 12v input.

works great now, so thats exactly what that wire was!

 

cool...

 

good to see you got it figured out

 

sheesh! just make your own harness...

 

that doesn't look like it would tuck behind the rear left tail light too nicely though, lol

but to you for actually soldering unlike most people and just crimping them!

 

i solder when i can...

thanks! here's the rest of the pics for the circuit, still waiting on a few parts

 

very cool!

I soldered everything with it came to my recent stereo install, but I got lazy on the trailer harness and just crimped


you ever used the program Express PCB for circuit layouts? it has a pretty nice schematic drawing program that you might enjoy although sometimes I can understand my schematics better if I draw them out on paper like you have there

 

yeah, i've made a few. it's easier for me to bread-board them and stick the components on proto-board. epic solder traces!

 

I didn't think anyone still used breadboards any more besides me

 

^^ sequencing led's? 555 on the left, 7--6 on the right?

 

was designing a circuit for alternating turn signals and running lights on my last truck on the far left a 5v regulating circuit since I was working off a 12v power supply, then yes a 555 timer to control the signal blinking during testing, and then a 7486 ic to make the outputs alternate


ended up ditching the ic all together when I figured I could use the filament bulb in the truck itself as a ground for the LED's I was installing for turn signals, so that simplified my circuit to just two rectifying diodes


yes I know these solders look horrible below, lol, but I was actually just getting into soldering

 

heh, they look a bit like my joints. i could do better if i weren't using a half-eroded 45w, but it works for the bulky connections.

anyway, i got the last bit of stuff today for my trailer wiring, so that should be ready soon.

 

yeah this thread got way off topic fast

I have yet to use the hitch or harness yet, but it's good to know that it's back there and working when the time comes

 

do you even have a trailer? you need to search craigslist for one