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Brake light on trailer wiring

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kleinchris
Join Date: Jun 2007
Posts: 269 Westminster, Texas
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2007-08-28          145153


Just bought my wife a new car and put a hidden hitch on it so she can haul around all my s***. I went to wire the lights and everything went fine except the brake lights. FOUR WIRES: LEFT TURN, RIGHT TURN, TAIL LIGHTS, GROUND. What am I missing? Can I wire the tail light wire to both the tailight and the brake light?



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Brake light on trailer wiring

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earthwrks
Join Date: Dec 2003
Posts: 3853 Home Office in Flat Rock, Michigan
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2007-08-28          145154


Be VERY careful about tapping into new car/truck wiring. Modern electronics are extremely sensitive to amp draw, and could result in damaged control module. On my '03 Ram which has a factory installed hitch and trailer package. All the trailer-related fuses are separate from the vehicle circuits. That means, say, if the truck's tailights don't work, the trailer's still will and vice versa.

I'd get a factory-approved trailer connector from the dealership which will have instructions.

BTW, you're missing the electric brake circuit (which means you'll need an electronic brake controller too), and the constant-on 12v circuit to charge the trailer's break-away battery if it falls into USDOT regulatory territory.
....


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Brake light on trailer wiring

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kleinchris
Join Date: Jun 2007
Posts: 269 Westminster, Texas
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2007-08-28          145156


this is a little 4x8 trailer- no battery back up for brakes. but brake light should still work right? ....


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earthwrks
Join Date: Dec 2003
Posts: 3853 Home Office in Flat Rock, Michigan
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2007-08-28          145160


On paper, maybe. LOL

Seriously, it depends on the type of circuit, namely if you have a similar type bulb that you're connecting to. It's been years since I have to cut-and-cobble (non-factory install) but I can remember having to use a separate electronic module that took the signal from the turn and stop lites (both single filament) on the vehicle (I think it was a foreign car that had separate turn and stop lites---I think). The module then transformed the signal to a usable one compatible to a single double-filament bulb. And you have to keep in mind that the stop lite may or may not be/have a running lite with a double filament or single if a running lite is also separate.

Again, it's much safer and easier to get a connector from the dealer that may even simply connect to a harness under the dash---and in some cases the trailer wiring is already run through the vehicle waiting to be connected to it. Another option is Hoppy. They are the major player in trailer wiring. I've used them before with great success. Tractor Supply carries them too. In most cases all you do disconnect the harness near the tailights, insert the Hoppy connector and reconnect the car harness (about 2 minutes total). If I'm not mistaken they also offer one of those electronic modules that manages the conflicting bulb signals--and (I think) it simply plugs into the Hoppy connector. Couldn't be simpler IMHO. ....


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Brake light on trailer wiring

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kleinchris
Join Date: Jun 2007
Posts: 269 Westminster, Texas
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2007-08-28          145161


Okay, I have figured it out, thanks to your help. The trailer brake lights work on both of my tucks becuase they have factory installed ports which is prewired to include brakes and tail light into one wire. On the new car, I'm only sending one signat through (in my case, the tail lights.) Can I double up the tailights and brakelights into one wire going to the trailer, or will I short something out? ....


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Brake light on trailer wiring

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JasonR
Join Date: Jan 2006
Posts: 142 Northern Indiana
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2007-08-28          145163


Are you asking:

you want to turn on both the brake lights and tail lights on the trailer when ever the the tail lights are on - on the vehicle?

- Jason ....


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Brake light on trailer wiring

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kleinchris
Join Date: Jun 2007
Posts: 269 Westminster, Texas
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2007-08-29          145164


yes ....


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Brake light on trailer wiring

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kthompson
Join Date: Oct 2005
Posts: 5275 South Carolina
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2007-08-29          145169


klien; check with your part's store as there are many adapters for 4 to 6 wire and 6 to 4 and so forth. Some (only have noticed this on SUVs and Pickups) that come from the factory with the plugs with both the 4 and 6 or 7 wired.
Earthwrks makes a good point you need to at least look at the ownners manual to see how it addresses trailer lights. Would hate to burn up a circuit and warranty become a major issue. You may find there is a kit that simply plugs into the factory wiring. kt ....


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Brake light on trailer wiring

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DennisCTB
Join Date: Nov 1998
Posts: 2707 NorthWest NJ
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2007-08-29          145172


Hi,

If you are talking about a new vehicle and not just new to you. The best thing to do is to use the auto manufacturer's trailer plug if one is already built into your car.

You then just buy the matching harness that fits that plug. I just did a Honda Pilot and a Honda CRV, could not be simpler. On my vehicles the harness comes with a module to take care of the separate red or yellow turn signals. Only takes a couple of minutes, and no worries about shorts etc.

Got mine at etrailer.com for about $25. I put the link in that takes you to the page where you look up your vehicle and get an exact fit harness. ....


Link:   eTrailer.com Vehicle fit lookup

 

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Brake light on trailer wiring

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DRankin
Join Date: Jan 2000
Posts: 5116 Northern Nevada
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2007-08-29          145176


Yikes! Stop what you are doing!

You can do thousands of dollars in damage to the numerous circuit boards that control almost every function in a modern vehicle. All it takes is one back-feed on the wrong wiring harness.

The days when you can just tap into wires has passed.

There is a custom engineered wiring harness available for you specific car of truck....... do yourself a big favor and get the proper set-up. ....


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Brake light on trailer wiring

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Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
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2007-08-29          145178


Mark is right, you can easily fry some spendy electric hardware crossing wires in a modern vehicle.

You can also do some pretty major MECHANICAL (read REALLY spendy) damage by connecting a few wires together wrong.

For instance, a lot of modern automatics use, amongst other things, the presence of 12 volts in the brake light circuit past the switch as a sign you are stopping and it is one of the triggers that unlocks the torque converter.

If your trailer harness back feeds the brake light circuit with 12 volts on such a vehicle, even at a low enough amperage that the lights don't come on, the torque converter will never lock up, and that together with the extra weight of even a small trailer can cause severe over-heating, this will shorten if not end the transmissions life. It will also likely void the warranty on said transmission.

Best of luck. ....


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Brake light on trailer wiring

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kleinchris
Join Date: Jun 2007
Posts: 269 Westminster, Texas
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2007-08-29          145183


Okay, I think you guys are thinking this is way more complicated than it is. This is a small trailer that does not have brakes, just brake lights. (No battery.) I am trying to hook up a four wire harness to a car. Blinkers work, tailights work, but the brake lights do not work. Besides the overwhelming advice to stop working on this car (which has been noted,) does anybody have any other ideas? ....


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Brake light on trailer wiring

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Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
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2007-08-29          145185


Ok, skipping the potential issues for the moment, a little more info. is needed to answer your question.

Is the vehicle equipped with a separate turn signal and brake light, such as the Japanese cars that have a yellow turn signal and a red brake light?

If that is the case, you need a 5 to 4 wire converter. It is basically a small set rectifiers (one way valves for electricity) and solenoids which allow the voltage to flow from the cars turn signal into the brake light circuit of the trailer and make it flash, without back feeding the brake lights on the car and making them flash too. These are available most any place that sells trailer wiring stuff such as auto parts places.

In a 'standard' 4 wire harness, the brake light flashes as a turn signal. In such cases the wiring is easier described as there being a ground wire, a running light wire, and a pair of brake light wires.

Best of luck. ....


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Brake light on trailer wiring

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kleinchris
Join Date: Jun 2007
Posts: 269 Westminster, Texas
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2007-08-29          145186


Murf, you are the man! Yes, I failed to mention that this is a Japanese car, and yes, seperate yellow turn signals. Okay, I am off to tractor supply and then I'm going to fry my wifes car. ....


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Brake light on trailer wiring

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Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
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2007-08-29          145187


If you haven't already started, I strongly suggest you spend the extra couple of dollars and buy the pre-made trailer converter, Hoppy is one of the biggest. I believe Draw-tite also make them, as well as several others.

The big advantage to these setups is they are about as simple as gravity, and use the factory harness connections. All you do is split apart a particular plug under the vehicle and plug in the T-fitting they give you!!!

All connections are then completely waterproof and guaranteed correct.

Best of luck.
....


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Brake light on trailer wiring

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kthompson
Join Date: Oct 2005
Posts: 5275 South Carolina
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2007-08-29          145189


Klein, sorry you missed Dennis and my comments on wiring options earlier. kt ....


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Brake light on trailer wiring

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DennisCTB
Join Date: Nov 1998
Posts: 2707 NorthWest NJ
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2007-08-29          145191


I also believe that if you hack up your wiring by splicing the lines your new car warranty may be voided by the dealer. ....


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Brake light on trailer wiring

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kleinchris
Join Date: Jun 2007
Posts: 269 Westminster, Texas
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2007-08-29          145195


I appreciated everybodies input, and if it appeared that I was missing information, maybe I wasnt giving enough. Murfs post seemed to contain the only info I could use right now. I need this thing tommorow morning, so dealerships and internet parts wernt an option. The part about foriegn cars having a seperate turn signal got my unstuck from where I was. TS had the part, and I am all fixed up. Except now my headlights won't turn on. Any ideas? ....


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Brake light on trailer wiring

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kleinchris
Join Date: Jun 2007
Posts: 269 Westminster, Texas
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2007-08-29          145196


Just kidding about the headlights. ....


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Brake light on trailer wiring

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earthwrks
Join Date: Dec 2003
Posts: 3853 Home Office in Flat Rock, Michigan
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2007-08-29          145210


Have you checked for a loose nut behind the steering wheel?

Kenny T. in SC has found the same loose nut behind the wheel of his pickumtruck for many years now. Iareckon he's taken a shine to himself...errrr...the ol' nut.

But he's a good nut.

Or was it that he had a loose screw? hmmmm ....


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kthompson
Join Date: Oct 2005
Posts: 5275 South Carolina
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2007-08-30          145227


EW, we found solution to the loose nut behind wheel of pickup here, very simple, no more Detorit built pickups...oh did not mean to hurt so badly.

Klien...was not trying to be rude and it came out that way sorry. Not looking back but thought Dennis only point out web best place to buy the item. I understand about Murf ability to point it out where it got your understanding. He has done that for me a few times. Also some times (man thing I know) the first time or two we just don't hear it or in this case read it. Glad you got it working. As to headlights, do you really need them on the trailer? :) kt ....


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Brake light on trailer wiring

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earthwrks
Join Date: Dec 2003
Posts: 3853 Home Office in Flat Rock, Michigan
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2007-08-30          145232


Kenny my "American" Dodge Ram was built in Mexico. ....


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