Ground wire help

[Filbert V.]

Okay, we installed the new trailer hitch on our 2008 Sierra which has the factory 7 blade connector, and we have the adapter from the 7 to the 4 flat configuration on the trailer end. We plugged it all in, had good brake lights, but when we turned on the right or left turn signal then both lights flashed so it looked like we were turning left and right at the same time. Upon further inspection, I see that my father had not connected the white ground wire which runs the length of the trailer to the rear bumper. Now do I grind off a small area on the frame underneath the rear of the trailer near the water tank, or connect the ground wire to the underside of the bumper where the two tail lights are mounted? Dad kept the original tail lights, but no wires are connected to them, so he mounted an extra set of round lights to the top of the rear bumper, and those are the ones which work. I'll keep the originals just for looks as I don't want to rewire the entire system at this point. Also, is there an option to self tapping screws for the ground wire? Any help and or photos would be greatly appreciated, as everything I found online only confused me more!

[Jack L]

Your lights would not work at all if you didn't have a working ground. You must have a pinched, or crossed or improperly connected wire somewhere in the system.

[Filbert V.]

So what do you think this extra white wire is doing attached to nothing? There is no ground wire mounted in the tongue area, and the only other wires to the rear are the yellow, green, and brown. This white wire must go somewhere, but where?

[Bob Miller]

I'd spend a few $$$ and get a trailer light plug tester and be sure that the TV wiring AND the 7 to 4 adapter is is correct. I have had defective 7-4 adaptors in the past.

Harbor Freight was selling entire stick-on trailer light sets for real cheap recently. These also make good test sets for ruling out the TV as a problem.

If you are near Riverside I have both of the above you can try out.

Off to one side is the possibility that the trailer has LED tail lights and, as it turns out, some of the OEM wiring adaptors don't like them because they don't draw enough current. Again, trying a different set of lights might provide a clue

[Francesca Knowles]

Originally Posted by Filbert V.

So what do you think this extra white wire is doing attached to nothing? There is no ground wire mounted in the tongue area, and the only other wires to the rear are the yellow, green, and brown. This white wire must go somewhere, but where?

White is definitely your ground wire, as it is in most of our trailers. I agree with your initial assessment that its lack of connection is the likely cause of your troubles. Ground is the first thing to check with ANY problem with trailer electricals, in my opinion!

I'm puzzled by your statement re. "no ground in tongue area"- doesn't the pigtail have ground? If so, it must be connected to something, and that white wire should be connected to that. If that proves true, it's your ground, and you probably need only to connect it to the lights to get things working.

[Filbert V.]

Well there are no TV connections, so that's out, and the second set of tail lights my dad installed are at least 20 years old, but the bulbs are still good as new. The 4 flat to 7 round connector is also new (came with the new hitch), and I just received a new 4 pin flat connector in the mail yesterday which I'll attempt to install on Saturday. By no ground in the tongue area, I mean there is no white wire that is bolted to the tongue. Looks like dad ran the ground wire to the rear along with the other 3 wires, and I just can't find out where he had it connected. My dad was much better at repairing things than I am, that's for sure! I was also thinking of buying that cheap set of magnetic lights at Harbor Freight to see if they work and then I'll just bungie cord them to the bumper, but then I'd have 3 sets of taillights, 1 working, and two for the show I guess.

[Francesca Knowles]

Originally Posted by Filbert V.

Well there are no TV connections, .

There must be- that's where the power comes from, right?

Your tug-side plugs are grounded to the tug. Plugging the trailer in to that pigtail connects trailer 12v ground to vehicle ground. That is, if the trailer groundwire is connected to the lights etc. Which it's not.

The disconnection of that groundwire may well be the cause of the original lights on the trailer itself not working, by the way.

[Bob Miller]

Tv = tow vehicle

And NEW does not equal "Works"

Been there, done that.

[mary and bob]

some newbies may be confused by " TV" or "tug" meaning the car or truck that is towing the trailer. Sounds like a simple ground connection but I'll refrain from further comment on that.

[Jack L]

In your initial post you said when a turn signal is activated both left and right turn signals flashed at the same time and you also said the brake lights worked. If you did not have some sort of a ground none of the lights would work. The white wire is usually the ground but with a previous owner working on it, who knows. I've seen trailers that used the hitch ball and coupler as a ground (very BAD idea ) and you may have a situation like that. If that is the case, adding a ground wire is a must.

Getting back to the issue of both turn signals flashing at the same time, there has to be an additional problem. You do need to make sure you have a good ground. If you did not have a ground connection, nothing would work. If you had a poor ground, things would work intermittently, but when both turn signals flash at the same time there is another issue

[Darwin Maring]

Ground the white wire to the frame and do another test.

Make sure the white wire on the tow vehicle is grounded to it's frame.
You can get a multimeter at Harbor Freight for less than $5 and sometimes free and you can get test plugs with lights for the flat and 9 pin connections there also.

I use one of those emergency battery packs that you use to start the vehicle to test trailer wiring. Connect the Black clamp to a good ground and then use a probe to test the individual connections. Connect it then go to the back to C what light is on.

Sometimes I use my wife to stand at the back however in most cases I get no answer because when I walk back there I find her pulling weeds or something else so I might as well just do it myself.

[aznative]

Ground Wire seems to be attached. If it wasn't then no lights would work. Might as well trace the wires on the trailer to see where they terminate. It seems to me that its the trailer but it can also be the new adapter. While at it make a chart like Green wire goes to driver tail light. And keep it in your trailer for future reference. Somewhere your right and left turn signal are connected at the plug or on your trailer. it may be obvious or it may be that the 2 bare wires are simply touching in a bundle of electrical tape. I've seen that plenty of times. Good luck. PM me if I can help you out. Also Invest in a multimeter it will take a lot of guess work when working with electrical.

[aznative]

[IMG]http://www.google.com/imgres?imgrefurl=http%3A%2F%2Fwww.accessconnect.co m%2Ftrailer_wiring_diagram.htm&tbnid=_UuijkUXJlk9i M:&docid=TToKcxgbFZFLwM&h=266&w=550[IMG]

[Darwin Maring]

Question: Does the 2008 Sierra use the same stop lite bulb for the turn signal or are they different bulbs?

[aznative]

I believe the GMC uses 3 bulbs per tail lights. So they are separate bulbs.

[Darwin Maring]

In that case, you may need the GMC trailer wiring harness or some kind of a converter like the foreign trucks use. Most american vehicles use the same bulb for stop and turn and the foreign trucks that have a yellow turn lamp require a converter for the american wired trailers so they will work. You should have someone work the brakes and turn signals and observe what is happening.

[Filbert V.]

I"m not sure Darwin, would it make a difference in something?

[Filbert V.]

Thanks for the TV lesson. I guess I'm more comfortable with tow vehicle! One of those lost in translation lessons. Now, would it be easier for me to just buy an entire new tail light kit from e-trailer or hitch anything, or will I still have problems between the tow vehicle and trailer? My electrical knowledge is sorely lacking.

[Bob Miller]

If you look for a plug-and -play harness it will come with a converter box to the flat-4 plug configuration if needed.

There are the ones that plug into an existing dedicated trailer light harness and others, with a "T" connector, that break into the existing tail light harness.

If you look your vehicle up on eTrailer.com I am sure you can figure out what's included with the different harnesses.

As far as I know, North American trailers always use combo turn and stop lights and get by with the standard 4 pin flat connector.

[Francesca Knowles]

Originally Posted by Filbert V.

Thanks for the TV lesson. I guess I'm more comfortable with tow vehicle! One of those lost in translation lessons. Now, would it be easier for me to just buy an entire new tail light kit from e-trailer or hitch anything, or will I still have problems between the tow vehicle and trailer? My electrical knowledge is sorely lacking.

This is as good a place as any to start learning- better than most, really. Since nothing's working right anyway, why not try to fix the original trailer lights? Someone posted a diagram on page one of this thread. I'd bet your trailer wires follow that color coding. And if they don't, the Scamp diagram in the document center here probably does.

Wiring in these teeny trailers is surprisingly simple. Even I have learned the system...and I'm one of those people to whom James Thurber's Mother's contention that empty light sockets leak electricity makes perfect sense!


If someone like me can learn to do it, surely you can. You DO have the advantage of that extra "Y" chromosome, after all...