Wiring Question

Well it has been confirmed. I am a complete Moron!!! Awhile back I posted a question about the wiring on my boat trialer, and got some good advise. However being the moron that I am I decided to rewire the whole thing. Keep in mind that I have never attempted such a thing.

I went out and purchased what I thought was the correct wire, and proceeded to remove the existing wire from the trailer. Now I’m not a complete idiot, just a moron, so I did snake the wire through, and hooked everthing up, and to my surprise it really was that difficult.

I hooked up the boat to the truck, and was so excited that I (the moron) could actually do this. I turned on the signal on the side that I knew worked prior to the rewiring, and it actually worked. Now the moment of truth. I turned on the other, and to my horror, it DID NOT WORK!!!! What the Heck could be wrong with this thing.

Soooo, a couple of beverages later, it hit me. Did I ever check for a blown fuse? Answer, NO!! I’m a moron, or quite posibly the Idiot that I claimed not to be earlier.

Now Here is my question, and remember to keep this as simple as possible.

I have lights on both sides, I have signal on both sides, But when I hit the brake, I only have one brake light, the other goes out. Why?

Thanks for reading, and please don’t be to hard on me. The wife is handling that quite well on her own.

Did you ever check the light bulb?? Or try other one’s. Sometimes you may have a front light out and it causes this problem.

If you have tail lights and signal lights are they a different intensity level? If so the bulbs are fine. Stepping on the brakes and having a light drop out sure sounds like a ground problem. Describe how the ground wires are connected to both the vehicle and the trailer. Do you have one of the cheapy volt/ohm testers to check signal at your vehicle connection? Best $10 you’ll ever spend.

Be sure everything is GROUNDED properly. Clean around all ground connections with a wire brush before connecting. Be sure you have the white wire on your vehicle grounded on your vehicle and the white wire grounded on your trailer. Many don’t use a ground, and then after the trailer ball rusts badly they have problems like you describe.

Hmm…on most trailers that I’ve seen the turn signal and the brake lights use the same wires and the same filament in the bulbs. The only thing different is that they BOTH come on when you hit the brakes. This means twice the current draw compared to one turn signal.
I’d check the ground side of things. Frequently “ground” is the frame of the trailer and that can involve several crusty mechanical joints. Makes sure you have clean metal-to-metal connections and that all of the bolts are tight.

The last time I re-wired a trailer I pulled a dedicated “ground” wire all the way back to the connector. That eliminated several sources of failure for me.

Good luck FB, it sounds like you’re very close to having this all working !

Rootski

I agree with Sarge, it sounds like a ground problem. I had something similar on an older trailer I was working on a few years ago. Is your trailer attached i.e., hitch on the ball) to your tow vehicle or are they just joined by the wiring? Are your ground wires on the triler contacting a nice piece of clean, exposed metal?

Brand new bulbs, and I switched them, and have the same problem.

There is a ground wire that goes from each of the taillights, to the trailer, and from the adapter connection to the trailer. I will check all of those, and see what happens. Thanks for the info.

I also agree with the bad ground. I once had a tilt trailer that wasn’t grounding at the point it tilted. I just run a seperate ground wire back to the lights.

JIM

Ground wire! Always the first culprit to look at!

A ground?

If the ground was bad, it would effect all lights, not just a single light.

Get a test light. That is the best method.

Also, what kind of vehicle is this? Vehicles with blinkers in their tail lights (like Ford minivans) require a special adapter to run trailer lights with single bulbs.

A bad ground makes the trailer act like it is possessed. If you think the devil is in your trailer, it’s probably the ground.

I had the same exact type of problem and it was the ground!

Another possibility, Check the adapter that plugs into your vehicle. My trailer has a 4 flat plug but my truck 6 a plug recepticle. The addaptor I use to reduce the 6 to a 4 went bad on me last year. I found that out AFTER putting on new lights and rewiring a new plug on the trailer and still had trailer light problems.
After figuring out the wiring was correct ( including the ground )and the power from the truck ( and fuses ) were cool that left the plug itself. When I took it apart sure enough a couple of the contacts inside it were coroded. Cleaned up the contacts , reattached the wires and problem solved.

Don’t be too hard on yourself. Wiring problems can drive anyone off thier rocker if your not familiar with the ins and outs. It was only dumb luck I figured mine out.

Ok, I’ll add my “Grounding Guess”.

In your original post you said you “hooked up the trailor.” I’ll assume you put the trailor on the hitch and dropped some weight to the tounge. If not, you may want to give that a try. Just hooking up the plugs will not ground your trailor properly.

-J.

Maybe. A flakey ground is going to act different depending on how much current is flowing through it. Applying the brakes will turn on the bright filaments in both bulbs, which would be worst case for current.

Rootski

Recommended reading:

Find the book called “The Grasshopper Trap” by Patrick F. McManus. On page 32 read the chapter called Trailer Trials”.

Actually, everything by McManus is incredibly funny.

Rootski

Hadn a similar problem on a BRAND NEW TRAILER. Turns out it was the 4-way plug that plugs into truck on the truck side not the trailer side. Bought new one and suddenly everything works. I did not re-wire trailer but spent over an hour troubleshooting it.

Rootski, I have that book, in fact, I have I think all of his books. I can usually only read one chapter at a time, because my eyes hurt from crying/laughing so damn hard.

Quote:

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Recommended reading:

Find the book called “The Grasshopper Trap” by Patrick F. McManus. On page 32 read the chapter called Trailer Trials”.

Actually, everything by McManus is incredibly funny.

Rootski

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Thanks for all of the tips guys. I am planning on looking at this again on Saturday, so I will let you know what I find out.

Did you also change the harness that comes from your wiring on your vehicle side. Call the local parts house or garage and they will tell you what wires to run to what side of the light. If all the wires are on the right posts it sounds like the ground in the light assembly that grounds each side of the light bulb. I ran a ground wire from the frame of my truck to the plugin then grounded the wire of the plugin too the trailer frame.

Well I got $.02 I can give ya.
1. culprit is like just about everyone said is the ground. When I suspect this I take a couple trips around the block so there is good contact through the ball. alot of times this clears up the problem but is not a fix just a confirmation.
But I just fixed one about 2 weeks ago that had those exact same symptoms. The trailer had the sealed light units that you can’t change bulbs you have to change the whole unit. It worked when that was the only one hooked up but when there were 2 it didn’t. Turned out to be the light unit itself was junk and it was only 2 months old.

Boat trailers are notorious for problems with grounds. When I rewire, I always run a seperate wire for ground from tow vehicle. Then I also run a seperate wire to all light brackets on the trailer. One should never rely on the ball coupler to be the ground. Then theres the corrosion problem because the light brackets are usually bolted to the trailer, and if it is a tilt trailer theres another bad connection. Just my $.02 Good luck

I too side with the guys running dedicated ground wires back to the trailer end of the plug. Then, after testing the car side of the plug, run a wire from the ground terminal to a good spot of bare metal (get out the grinder if you have to) on the truck frame. And make sure to use a good quality ring terminal and either solder of heat-shrink-tube wrap all connections. I have gone as far as to temporarily run a wire directly to the negative battery post when troubleshooting.

Here’s a link with some good info for you to check out:

http://www.blueox.us/Accessories/gremlins.html

Although it is realted to towing a vehicle behind a motorhome, it has some info on taillight converters, as well as troubleshooting procedures.

Make sure the trailer is grounded properly to to your tow vehical too.

One quick tip for troubleshooting is to spray the ball with WD-40 before hooking on the trailer. If the problem goes away or changes then it is definitely a grounding problem.

Bad ground could also be at the light, not necessarily the truck.