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Old 12-08-2007
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Need help - ground wire on trailer switched polarity?

A couple of months ago, I accidentally ripped out the wires from the plug on my stock trailer. Its a 7 slot receptacle with the usual red, black, brown, yellow, green and blue wires. When I wire it up according to the diagram I found here: http://www.etrailer.com/faq_wiring.aspx nothing works correctly.

BY THE WAY, THE TRUCK I AM WORKING WITH IS THE BRONCO.

After a bit of playing around with the wires, I found that the green and yellow wires needed to be switched around. Now the driver's side is working fine, however the passenger's side of the trailer is not. After trying to work out the problem, I dragged a wire grounded to my truck to the passenger's side ground on the trailer, and found that the light works fine if I replace the ground.

Here's the odd part, when I touched the ground wire I created off my truck to the ground wire on my trailer, it sparked every time.

[//b]Sorry for all the blabbering, now for the questions[/b], how the hell can a ground, directly on the trailer turn positive? And how can I reverse it back to being a ground again so I can get the light to start working correctly again?

Last edited by winks; 12-08-2007 at 02:36 PM.
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Old 12-08-2007
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According to that diagram and what wires you listed your missing the white wire for ground since you only listed 6 wires unless its using the black wire for ground.

Term. 1 should be ground (white wire)
Term. 2 should be trailer brakes if used (blue wire)
Term. 3 should be trailer tail lights (brown wire)
Term. 4 should be 12V Aux power if used (red/black wire)
Term. 5 should be left turn (yellow wire)
Term. 6 should be right turn (green wire)
Term. 7 should be Aux Power if used (orange wire)

I would back prob the vehicles receptacle making sure all wiring has the proper feeds plus ground and is on the correct term. If that checks out, then I would run a temp ground to the trailer from the vehicle (jumper cable etc.) and then run a temp fused power feed from the battery and touch it to the brown then yellow and then green wires on the trailer to verifiy that the park and turn signal bulbs light up and are wired correctly. All of these should ground through the trailers frame.

If all checks ok then its just a matter of properly wiring the trailer plug to match the vehicles receptacle.

Note, if the trailer is missing a ground and you have power going to the lights and then connect a ground from your vehicle to the trailer frame it may spark. This is because the lamps are not loading the circuit and the frame is hot, i.e., 12 V before and after the bulb. Once you complete the circuit to ground the bulb becomes the load and drops the voltage potential to 0 after the bulb.
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Old 12-08-2007
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Rev, the white wire is actually the black wire in my setup. The only wire I don't have is an orange wire, which is for the axillary lights. My trailer doesn't have any connections for that.

As for your ground idea, I did that as well, and found that all my grounds coming off the truck are fine, as well as all of the grounds that go to my trailer plug are fine. The one ground that is not fine is the one coming off the trailer to the light.
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Old 12-08-2007
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Quote:
however the passenger's side of the trailer is not. After trying to work out the problem, I dragged a wire grounded to my truck to the passenger's side ground on the trailer, and found that the light works fine if I replace the ground
It sounds like the passengers side lamp has a bad ground to the trailers main frame. Is any part of it or the lamps mounting insulated from the trailers main frame? How is the lamp grounded?
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Old 12-08-2007
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That is the case, it is a bad ground to the passenger lamp. The ground is simply a 6" wire riveted to the frame, connecting only to the lamp. I have no idea how it could have become a bad ground, there are no cuts in the wire for it to connect to anything hot.
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Old 12-08-2007
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so, are the lights on when your hooking the ground up?

lol...
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Old 12-09-2007
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Quote:
The ground is simply a 6" wire riveted to the frame
If thats where you touched the ground from your vehicle when it sparked and the the light came on I would suspect theres some corrosion around the rivet. You can confirm this with an ohm meter. With the trailer unplugged from the vehicle, check for continuity between the rivet and the trailers main ground point. If the meter shows an open circuit, drill out the rivet get a self taper and star washer to replace it.

Quote:
there are no cuts in the wire for it to connect to anything hot
If its not grounded (open circuited) to the frame then the wire coming from the lamp would in a since be hot until you ground it. If its in fact a bad gound at the rivet and you were to take a reading with a volt meter you would see 12V on the ground wire coming from the lamp.

Last edited by Rev; 12-09-2007 at 01:27 AM.
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Old 12-09-2007
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Originally Posted by 5speedin2.3
so, are the lights on when your hooking the ground up?

lol...
I tried so many scenarios, I probably even hooked my truck up to my fiance's Ford Escort and didn't even realize it.

Rev, thanks for the info. I don't plan on getting back to working on the trailer for a while, but that is some good info I'll put to use when I go at it again.
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Old 12-09-2007
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well, if you hooked the ground wire up while the lights were on, its going to spark.
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