Trailer Lights . . . . HELP!

[HavasuDreamin']

The Problem: All running lights work fine, but when I hit the brakes, ALL of my trailer lights go dead. When I let off the brakes, they come back on. Turn signals work, but the light on the other side flashes from dull to a little brighter almost as if it is cutting in and out (both sides have the same problem when the opposite blinker is on).
The set-up: This is a 20-year old custom boat trailer in decent shape (aside from the lights). It is a box trailer with the wiring running trough the tube so I can't see the condition of the wiring. I have two lights out back, one on each side. Each light has two wicks. I assume one is for running lights and the other for turn signal and brakes. I also have four marker lights, two on each fender, one in front and one in back.
My thinking is that I most likely have a wire or two mixed up . . almost as if the wire for my running lights is hooked up to my brake light wire, thus when I hit the brakes, all goes dead. However, I have tried every wire combination possible from my truck to my trailer and nothing works right. Or . . I might have a bad ground on my truck. However, the lights worked fine in the past and I haven't touched a thing (except it was repainted and for some reason I had a lot more slack . .able to extend my wire out the back of my truck a lot further when I got it back)?
I have worked on this all day! Please help. I have resorted to drinking to ease my frustrations http://free.***boat.net/ubb/biggrin.gif

[intense]

You have a bad ground circuit, easy fix.
intense

[ratso]

intense is right...trailer ball may be rusty. Take some sandpaper and scuff up the ball and the inside of the coupler and I bet they will work.

[737jetmech]

Check the ground at the lights as well... I had the same thing and found a bad ground at one of the tail light assemblies. Good Luck! Bob

[jroos]

Bad ground. My advice. Iftrailer and wiring are 20 yrs. old, CHANGE WIRING COMPLETELY along WITH EVERY LIGHT ASSEMBLY.
I guarantee you won`t have any more problems.
Remember to stick the contacts of the bulbs in grease(Auto Zone).

[HavasuDreamin']

So it is a bad ground then for sure! Great, I should be able to fix this! Is it a bad ground on my trailer or should I be looking at the truck. Like I said before, I don't think it is the truck since I haven't messed with it and it was working before, but want to double check.
More Info: My trailer is wired to a chrome "four prong" switch up front which is mounted on the trailer. I have a separte piece of which the four prong male component plugs into the trailer and the other end to the truck (standard black plastic connector with three prongs and the ground). Thus, I have a 24 inch piece that disconnects from both. The chrome four prong piece that is attached to the trailer does not have a ground wire (I assume the trailer ball mount grounds the rig). The ground from the black connector that attaches to the truck has no where to go, so I wrapped it in electrical tape and did not attach it to anything (no ground on the four prong connector). Any thoughts on what I should do if sanding the trailer hitch ball and coupler does not work?
I don't want to re-wire the trailer unless all esle fails. Reason, the wires run inside the box trailer rails and if I pull new wire through, it will be next to impossible to get my running lights on my fenders attached to the new wire. Any more insight as to what I should do in the event the trailer hitch sanding doesn't work would be great. By the way, all running lights are new with the exception of the right rear tail light. Thanks!
[This message has been edited by HavasuDreamin' (edited March 24, 2002).]
[This message has been edited by HavasuDreamin' (edited March 24, 2002).]

[intense]

The bad ground is on the trailer. Make sure each light has a good ground and that the trailer main ground is good. You said the trailer was repainted, there is your problem. Make sure the grounds are to bare metal and clean.
intense

[ratso]

HD: If the rest of the wiring is hooked up right, it has to be a ground, the trailer is grounding thru the ball and hitch. I do not know what you drive but you might check the wires with a test light. In a lot of cases on your wiring you will use brown for tail, yellow for left, and green for right, and your brake lights will work as long as you don't have the seperate bulb for turn signals. Best I can do without more info.

[HavasuDreamin']

My mistake, the truck was repainted. I don't think they messed with the trailer light assembly, but I had a lot more slack in the wiring harness (truck) when I got it back. I will re-do the grounds on each tail light and sand the coupler and ball. If that doesn't do the trick I will be back on the boards posting.
Right side of trailer is green wire and brown, left side is yellow and brown. The separate 24' piece connecting the truck and trailer as previously stated is the standard black plastic, one brown, green, yellow, and white (gound not connected as there is no place to connect on the four prong attached to the trailer. Truck is an '88 full size chevy 2500 with trailer tow package. Any other thoughts! Thanks. http://free.***boat.net/ubb/cool.gif
[This message has been edited by HavasuDreamin' (edited March 24, 2002).]
[This message has been edited by HavasuDreamin' (edited March 24, 2002).]

[Hawaiian 93]

having had a welding/trailer shop now for over 10 years I will tell you that ground is 90% of the lighting problems. In your case I would say 1) get the ground on the truck on. I am sure that you have a receiver and there is just to many places for it to not ground well and that makes it a have to on useing the ground wire.

[HavasuDreamin']

Hawaiian, not sure what you are saying? Are you saying to make sure the ground on the truck's trailer light assembly is attached? If it is not, what can I ground it to the frame or hitch receiver?

[ratso]

HD: Take a jumper cable, make sure to get a good ground and hook one end to your trailer, the other end to your truck bumper or frame, and check the lights. If it is a bad ground, the lights should now work.

[HavasuDreamin']

Right on! A sure fire, quick easy test to diagnose the problem. I am not going to get a chance to test it for a few days, but I will let you know the results a little later this week. Thanks to all who responded, I now have new ideas to try instead of banging my head against the wall! http://free.***boat.net/ubb/cool.gif

[jroos]

You have to ground the wiring harness to the trailer. Use I believe the white wire for this.
If the harness from truck is longer, they probably cut the 210 zip ties that held the excess bundle in place somewhere under the bed to take out tail light assemblies for paint. But recheck that ground. Do you have surge brakes? If so I a similar problem. EVERY light assembly HAS to have a GOOD ground.

[ratso]

HD: if you can't get it now, pull that sucker down to Texas and I'll fix it for FREE!

[dankirk]

Your lights are getting their ground through the brake light circuit. When you step on the brakes, that ground goes away and switches to positive voltage and your lights go out. You need to ground your trailer. Don't trust the ground through the hitch. Your plug has four pins, right, left, running, and ground. If your ground wire is missing from your plugs, run a new one. All you need to do is take apart the 4-pin plug from your trailer, add the missing ground wire to the plug, and connect the other end of the ground wire to a clean, unpainted spot on your trailer. If you try to rely on your hitch grounding your trailer, you will have a bunch of intermittent problems with your lights. Good luck!
[This message has been edited by dankirk (edited March 24, 2002).]

[CoastGuardSteve]

HD,
dankirk hit the nail on the head! using the ball as your only source for a ground will give you fits that will cause your rectum to bulge. Honestly though, you could cruise to your local parts house and pick up a new split trailer harness for less than $20 and a couple packages of scotch locks and kiss your troubles good-bye. Don't worry about the trailer having a closed tubing design, just cut your old harness at the Y and use it as a phish for your new harness. Don't cut your new harness up.
Hope you get it whipped,
Steve

[Oldsquirt]

HavasuDreamin', here comes my two cents worth.
Since the truck has been repainted, verify that ALL lights on the truck work and work properly. Remember, brake lights must be brighter than the taillights. If anything doesn't work, correct it first.
If they are OK, go to the trucks trailer connector and verify that everything there is working right. Make sure the ground at that plug is connected to a clean ground on the truck's chassis. Note: you can buy a handy trailer plug tester at any decent auto parts store. Makes testing a breeze. Just plug it in and watch the lights.
If everything is good so far, it's time for the trailer. Do whatever is necessary to provide a WIRED ground to trailer. Like everyone else has said, the hitch and ball are not an adequate ground circuit. Once done with that, retest all lights. If problem still exists, and I have a feeling it will, go straight to the trailer taillights.
Since you didn't mention a white wire running down either side of the trailer, I wonder if they simply grounded the lights to the trailer instead. Might be OK when new, but possible problem after 20 years of use. I assume the trailer has the sealed, submersible lens/bulb assemblies that are held in place by a rubber grommet. Pop them out and visually inspect the wiring. If it looks good, disconnect the bulbs and measure the voltage between the brown and white terminals with running lights on. Should be near battery voltage. If OK, try new bulb(s).If not, measure voltage between brown wire and clean metal on trailer. If this shows battery voltage, then you need to repair the taillight ground circuit. How you do that will depend on how the wiring is run and how much(or little) work you are interested in.
Hopefully this will help resolve your problem.
OLDSQUIRT

[HavasuDreamin']

Thanks again for all the replys! Like I said before, unfortunately I am not going to get the chance to work on it for a few days, but I will let you know what happend after I have the time to rip into it again!
HD -out!