Need help re-wiring my trailer!

[NYBo]

Re: Need help re-wiring my trailer!

The adapter doesn't need the center contact, so that's why there isn't one.

It sounds like the harness on the truck isn' wired correctly, meaning it's not from the factory.

 

[thepotroast]

Re: Need help re-wiring my trailer!

You got the right adapter....it's a 7 to 4 adapter. I use the identical one on my rig which comes with the factory 7 wire RV hookup on the class 3 tow hitch, and I needed to have a 4-wire flat hookup. Your adapter is correct.

 

[Biggems]

Re: Need help re-wiring my trailer!

Ok so I have the correct adaptor.

So you think the wiring on my truck is wrong? Man this is getting really complicated for a noob! lol

 

[NYBo]

Re: Need help re-wiring my trailer!

Get yourself a cheap 12V test light and check the connector on the truck as per the diagram here:trailer lighting diagrams
Scroll down to the 7-way car end diagram. Note that the contacts labeled "Left Turn" and "Right Turn" are also used for the brake lights. Test the contacts under all possible lighting situations: taillights on, taillights off, brakes on, brakes off, turn signal on, turn signal off, and all combinations of these. If it all checks out properly, test the four poles with the adapter plugged in to eliminate the unlikely possibility you got a bad one. If that checks out, the problem is in the trailer. A bad ground is the most common problem.

 

[Biggems]

Re: Need help re-wiring my trailer!

Forgive my noobness, but I just realized that the adapter has test lights on it. (here's a pic) It has 3 lights labled "L", "R" and "T". I'm assuming that stands for "Left", "Right" and "Turn". I just went outside and hooked it up to the truck and turned on the lights and the only light that came on was the "T".

So I guess this means I have to disect the vehicle's wiring now?

 

[gunner1]

Re: Need help re-wiring my trailer!

This is gonna sound dumb- but is the round plug adapter in the factory plug the right way? On my Silverado, there is a large "groove" that the plug adapter slides into with it's corresponding "raised" section. Kinda hard to describe. Maybe try removing the plug and rotating it 90 degrees and see if it will still go in. Don't worry- these trailer lighting problems are usually VERY easy to fix- just don't lose your head.!

 

[Biggems]

Re: Need help re-wiring my trailer!

lol yeah its going in the right way. There is only one raised portion of the adaptor therefore there is only one way it can fit in.

 

[NYBo]

Re: Need help re-wiring my trailer!

Forgive my noobness, but I just realized that the adapter has test lights on it. (here's a pic) It has 3 lights labled "L", "R" and "T". I'm assuming that stands for "Left", "Right" and "Turn". I just went outside and hooked it up to the truck and turned on the lights and the only light that came on was the "T".

So I guess this means I have to disect the vehicle's wiring now?

That would be "left", "right", and "taillight".

Sounds like the truck's harness is the problem.

 

[Rocky_Road]

Re: Need help re-wiring my trailer!

That would be "left", "right", and "taillight".

Sounds like the truck's harness is the problem.

Just the opposite...he is good, "T" (taillights) glowing with the truck lights on. This "T" terminal should mate to the brown wires on the trailer.

The "L", and "R", will light when the respective turn signal is used. They both will light when the brake is applied....

 

[NYBo]

Re: Need help re-wiring my trailer!

Just the opposite...he is good, "T" (taillights) glowing with the truck lights on. This "T" terminal should mate to the brown wires on the trailer.

The "L", and "R", will light when the respective turn signal is used. They both will light when the brake is applied....

Well, a dope slap for me! Of course he needs to see what happens when the brake pedal is hit and the turn signals used. D'oh!

 

[kamby]

Re: Need help re-wiring my trailer!

Hmm, usually on a vehicle fairly new they have a wiring kit that you detach the factory plug harness and attach the wiring kit and the factory wires go on either end. If he's wired for trailer breaks there will be a blue wire usually running to it from the trailer break box, or under the dash if one wasnt included.

You may want to check were it plugs into the vehicles wiring harness and make sure nothing is burnt out or corroded. no broken wires etc, if there is a bunch of cut wires then it was self wired, nothing wrong with that but make sure all wires are connected properly. Also make sure the ground is attached underneath the vehicle tight, i've seen them come lose and cause intermitent ground problems. Also check for freyed or worn wires underneath as well.

Just some thoughts

Here is a link to a wiring harness adapter

http://www.etrailer.com/pc-VWH~118334.htm

 

[Biggems]

Re: Need help re-wiring my trailer!

Yesterday when I put the adaptor in, I also turned on the turn signal and nothing changed as far as the test lights. Only the "T" light was on. However, when I had it hooked up to the trailer, the turn signals did work.

I haven't tried hitting the breaks with the test light though.

I took a quick peak under the back of the truck and it looks like the harness was either done in the factory or professionaly done. It's going to be a pain in the arse to figure out where the problem is.

 

[Biggems]

Re: Need help re-wiring my trailer!

ok here is the latest...

(On the adaptor) When the lights are on, the "T" light comes on. When you push the breaks, all the lights come on. When you hit either turn signal, the respective light flashes. However, it's extremely dim and it can barely be seen. I didnt even notice it the first couple of times.

I went back today and spliced the running lights into the brown wire on each side. They work.

When I hit the breaks, all the lights on the trailer still go out. and when I turn on either turn signal, both rear lights flash alternately. almost as if they were the emergency flashers but they dont flash together, its one after the other. It's the same thing with either turn signal.

Here is a picture of where I have the ground wires connected for each of the tail lights. Is this ok? Sorry its so small

 

[Rocky_Road]

Re: Need help re-wiring my trailer!

ok here is the latest...

(On the adaptor) When the lights are on, the "T" light comes on. When you push the breaks, all the lights come on. When you hit either turn signal, the respective light flashes. However, it's extremely dim and it can barely be seen. I didnt even notice it the first couple of times.

I went back today and spliced the running lights into the brown wire on each side. They work.

When I hit the breaks, all the lights on the trailer still go out. and when I turn on either turn signal, both rear lights flash alternately. almost as if they were the emergency flashers but they dont flash together, its one after the other. It's the same thing with either turn signal.

Here is a picture of where I have the ground wires connected for each of the tail lights. Is this ok? Sorry its so small

Did you ever get around to properly grounding the white wire at the trailer tongue? Make sure that there isn't ANY paint between the lead, and the trailer....

Sooo many trailer lighting problems turn out to be a grounding issue...!

You may also consider replacing, or upgrading, your turn signal flasher unit? I just did a Google search, and there have been a ton of problems with your car model's turn signal flasher.

 

[Biggems]

Re: Need help re-wiring my trailer!

No I haven't yet properly mounted that ground wire to the trailer. For the test, I just wrapped the wire around the hitch on the back of the truck. That would suffice wouldnt it?

Also I just noticed, and it may be hard to see in the picture, but the place that I mounted each ground wire for the tail lights (on the back side of the frame where the lights are mounted) is painted. So i'm assuming i should get rid of the paint right there? whats the best way to do that? sand paper?

I'll look into replacing/upgrading my turn signal box in the truck. But as of right now I have no money!

Also, I bought a cheapo toolkit the other day at advanced auto parts and it came with a light tester. However, I have no idea how to use it lol. It looks like a metal pen with a small wire that I plug one end into the top of the pen and the other end has a clamp. I'm assuming this is the ground so I attached that to the hitch and then touched each prong on the vehicles harness with the pen but nothing happened? is the thing supposed to light up if it is getting juice or what? and yes the vehicles lights were on.

 

[Rocky_Road]

Re: Need help re-wiring my trailer!

No I haven't yet properly mounted that ground wire to the trailer. For the test, I just wrapped the wire around the hitch on the back of the truck. That would suffice wouldnt it?

Also I just noticed, and it may be hard to see in the picture, but the place that I mounted each ground wire for the tail lights (on the back side of the frame where the lights are mounted) is painted. So i'm assuming i should get rid of the paint right there? whats the best way to do that? sand paper?

I'll look into replacing/upgrading my turn signal box in the truck. But as of right now I have no money!

Also, I bought a cheapo toolkit the other day at advanced auto parts and it came with a light tester. However, I have no idea how to use it lol. It looks like a metal pen with a small wire that I plug one end into the top of the pen and the other end has a clamp. I'm assuming this is the ground so I attached that to the hitch and then touched each prong on the vehicles harness with the pen but nothing happened? is the thing supposed to light up if it is getting juice or what? and yes the vehicles lights were on.

You have GOT to get that front white wire securely grounded, before we go any further in this wiring diagnosis! Find a bolt on the trailer tongue area, that you can use this wire with.

The grounds at the lights should be fine...in theory. But I have found that to be sure, you have to scrape some paint away where they touch the frame...you can't rely on the light stud to do the job. Just take an old kitchen knife, and scrape away!

Your light tester can only detect a 'live' circuit...use it on the flat plug end of your adapter to verify that you are getting voltage on each pin, as you turn on each of your truck lights (running and turning/brake). Here are some pictures of a common circuit tester...yours should be similar:

 

[Biggems]

Re: Need help re-wiring my trailer!

The reason I haven't permanently fastened the ground wire at the tongue yet is because I dont think it's long enough. I'll probably have to add some wire to it. But I'll do that first thing next time I go out.

My light tester isn't nearly as nice as that one haha. My "pen" is all clear so I can't tell if there is a light in there that is supposed to come on or where it is. I grounded the wire to the hitch and touched each prong in the harness with the tip of the pen but didn't see anything happen. Maybe it's just a really dim light or I got what I paid for and the POS doesnt work! ha.

 

[kamby]

Re: Need help re-wiring my trailer!

The reason I haven't permanently fastened the ground wire at the tongue yet is because I dont think it's long enough. I'll probably have to add some wire to it. But I'll do that first thing next time I go out.

My light tester isn't nearly as nice as that one haha. My "pen" is all clear so I can't tell if there is a light in there that is supposed to come on or where it is. I grounded the wire to the hitch and touched each prong in the harness with the tip of the pen but didn't see anything happen. Maybe it's just a really dim light or I got what I paid for and the POS doesnt work! ha.

The trailer plug (plug that plugs into the vehcile cable) is usually mounted within a foot of where plug is, drill a hold screw it to the frame. You can not rely on the hitch to provide the ground for the trailer, if the frame is rusty or something than its not gonna provide a good ground to the hitch,since hitches are painted there is very few bare metal spots for the hitch to ground with the frame ground. If you use the ground coming out of the 4 way flat than is a direct wired ground to the vehciles ground rather than rely on a frame. I was working on the license plate light on my 72 gmc and the bumpter was so rusted it would nto all the ground the light to work, i had to scrap a lot of rust of to get the light to work.

Another thing too you may have to up the fuse for the turn signals and upgrade the flasher to a heavy duty one, if you have a weak flasher than they dont work right.

As far as all the lights going out when you press the break pedal sounds like a short somewhere, look at the adapter do the lights go out on the adapter when the break is pushed... if they do check the vehicle, could be why your having a problem cause it grounding to the frame there is a short when the breaks are pressed causeing the ground to energize casing the lights to go out.
if not, look for a broken wire on the trailer somewhere.

 

[Rocky_Road]

Re: Need help re-wiring my trailer!

The reason I haven't permanently fastened the ground wire at the tongue yet is because I dont think it's long enough. I'll probably have to add some wire to it. But I'll do that first thing next time I go out.

My light tester isn't nearly as nice as that one haha. My "pen" is all clear so I can't tell if there is a light in there that is supposed to come on or where it is. I grounded the wire to the hitch and touched each prong in the harness with the tip of the pen but didn't see anything happen. Maybe it's just a really dim light or I got what I paid for and the POS doesnt work! ha.

Pop the hood of the car, and do what I did in the picture...clamp the truck battery's negative post, and touch the positive post. That will determine if your tester light bulb is even working, and just how bright it will be.

Going to catch some 'ZZZ's...so I can get up early enough to use the morning high tide to make it into the Gulf! I've hit bottom so often, that I am tempted to name my boat "Runaground Sue"....

Later!

 

[Biggems]

Re: Need help re-wiring my trailer!

Good idea. I'll test it with the trucks battery to see if the piece of crap even works!

As I mentioned in an earlier post, with the adaptor plugged into the vehicle, when I hit the breaks, all 3 lights come on nice and bright. But when it is plugged into the trailer, all the trailer lights go out (trucks break lights still work) When I just have the regular lights on. Then the "T" light on the adaptor is on nice and bright. It's just when I hit either turn signal, the respective test light flashes, but extremely dim.

Maybe I do need a heavy duty flasher. Autozone? walmart? how much is that going to set me back? hard or easy to do? I am very much a noob!

As far as any wires being broken, I really doubt it as I just replaced all the wires with brand new ones.

Just to recap; when the trailer is hooked up to the truck, and I turn on the lights, all the lights come on and work fine. It's just when I hit the breaks they all go out and when I use either turn signal, both trailer lights flash alternately.

It's a beautiful day here so I'll see if I can run back out there today to properly mount the tongue ground wire and also see if I can get that test light to work.