tail lights - wired incorrectly? - Fiberglass RV


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Old 07-07-2008, 05:04 PM   #1
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So the project is going very well, but I noticed the taillights seem to run backward. When the headlights/running lights are on, the taillights are nice and bright. Applying the brakes, however, only results in a short blink. Nothing brighter. With headlights/running lights off, I see that the brakes activate the dimmer of the two elements.

Seems to me the running lights should be dim, the brake lights should be bright.

I've checked the existing wiring. Here's what I have:
brown wire from four-wire harness attached to the only black wire that extends from the light housing. (The light offers only one black wire and one white wire.)

How does the bulb "know" whether to light the dim or bright element? How can I reverse this.

In a related issue, there are four marker lights on this trailer. They are all this type. Like the other lights, this one comes with two wires (one white, one black). When hooked up (white ground, black hot), only one of the bulbs will light. All four of these lights do this. I've checked the bulbs and they all work, but only half of the "outlets" actually work. What's up?

Electrical...my first real headache.



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Old 07-07-2008, 06:35 PM   #2
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there normally are two wires on a stop/turn tail light, a red and a black.
the red is the stop or turn function and the black is the running light function. it is assumed they are mounted to a metal frame which carries the ground. Otherwise you need a ground wire as well.
If the bulbs in your taillight don't have two little filaments, they may not be a stop light, only a marker instead. If you look inside the socket, there should be two little contact bumps

The marker lights should be wired with one wire to ground, with the cover off, you should be able to tell which one goes to the bulb tip (white on mine), and which one goes to the body of the marker light (black on mine).

These colours may not match what you have so check closely.

If you have a multi-meter or continuity tester, take the bulbs out, put one lead on the shell for the light, and the other lead on the metal shell the bulb sat in. When you get continuity (or 0 ohms)that is the wire to use for ground. the other would be the hot, and should contact the tip of the bulb.

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Old 07-07-2008, 07:26 PM   #3
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Quote:
1. [b]Seems to me the running lights should be dim, the brake lights should be bright.
2. I've checked the existing wiring. Here's what I have:
brown wire from four-wire harness attached to the only black wire that extends from the light housing. (The light offers only one black wire and one white wire.)

How does the bulb "know" whether to light the dim or bright element? How can I reverse this.

3. In a related issue, there are four marker lights on this trailer. They are all this type. Like the other lights, this one comes with two wires (one white, one black). When hooked up (white ground, black hot), only one of the bulbs will light. All four of these lights do this. I've checked the bulbs and they all work, but only half of the "outlets" actually work. What's up?
It sounds (to me) that you have stumbled upon the "Secret Code" of trailer lighting fixtures.
I found this out several years ago when I was rebuilding a Compact Junior Trailer. The light fixture manufacturers leave out an important piece of information! The vehicle manufacturers know this fact, but trailer owners who want to do their own work aren't privvy to this ommission and are stymied by it.

In a [b]4-pin flat trailer harness, the wires are color coded like this:

White = "Ground" (circuit return)
Brown = "Running Lights" (dim filament)
Yellow = "Left Turn/ Left Stop" (BRIGHT filament on the Left Side)
Green = "Right Turn/ Right Stop" (BRIGHT filament on the Right Side)

Here comes the [b]SECRET of the Secret Code:
The Light Fixture Manufacturers all ASSUME that the Light Fixture will be installed ON the Metal Frame of the trailer. [b]OR They ASSUME that the Light Fixture will be installed on the Metal Skin of an Aluminum Trailer; this skin is assumed to be screwed onto the Metal Frame. Because the frame and skin of a metal trailer is ASSUMED to be GROUNDED, The manufacturers NEVER give you a separate Ground Wire!

Quote:
(The light offers only one black wire and one white wire.)
These are BOTH "hot" wires! One is for the dim filament, and one is for the BRIGHT filament.
I have forgotten which is which. Your statement (#1 in the quote above) is CORRECT.

Because Fiberglass Trailers' "skin" is non-conductive, the light fixture cannot be grounded by the mere act of screwing it or bolting it to the body of the trailer in the same way it works on a metal trailer. [b]You have to run a separate grounding wire and connect it to the metal base of the light fixture!

Once you figure out which provided wire is for the BRIGHT circuit, and which provided wire is for the dim circuit, you'll wire thusly:

White = your added grounding wire to the fixture's metal base on BOTH sides
Brown = Whichever wire is the dim circuit on BOTH sides
Yellow = Whichever wire is the BRIGHT circuit on the LEFT Side ONLY
Green = Whichever wire is the BRIGHT circuit on the RIGHT Side ONLY.

When you turn on your Left Turn Signal, the Yellow circuit will be completed thru the flasher.
When you turn on your Right Turn Signal, The Green circuit will be completed thru the flasher.
When you step on the Brake Pedal, Both Yellow AND Green Circuits will be completed.
When you turn on the running lights, the Brown circuit will be completed.
The White wire is the return path to complete any of the above circuits.
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Old 07-07-2008, 11:15 PM   #4
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Another odd part about the Reflect-O-Lite 650 tail lights on my Compact Jr. is that there are three bulbs. Two are single filament and one is double filament. I assume that one single is a tail light and the other is a turn signal. The double is a brake and a ??? I never could get the system to work right. I resorted to an unorthodox solution. I altered the wiring in the trailer by adding another wire. I added a 5 flat plug to the tow vehicle which has seperate brake and turn circuits. I now have a ground wire, brake light wire, tail light wire, left turn wire and right turn wire in the trailer. It all works correctly.

When I replaced the old lights (due to a lost lens), I had to add a bulb and holder to the new Bargman 92's. Strange system but it works.

Tom Trostel
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Old 07-07-2008, 11:28 PM   #5
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If you've rewired the trailer you'll need to run a wire from the negative side of the system (Notice I didn't say ground, since ground is often confused with the trailer frame. )

If you're using existing wiring there should be a third wire at the fixtures.

Fredric is correct. The only thing I would say is don't get hung up on the wire colors. If you or somebody else has rewired things the colors could be anything. A good volt meter will help sort it all out.
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Old 07-08-2008, 03:50 AM   #6
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Once you figure out which provided wire is for the BRIGHT circuit, and which provided wire is for the dim circuit, you'll wire thusly....

Strangely, this all makes COMPLETE sense! Thanks for clarifying. I feel SO much better now! (I'm NOT a moron afterall!)

It seems the previous owner did stick with the color code (largely) in rewiring, so I'm headed to hardware store in the a.m. to get myself a supply of matching colors. (Hey, what can I say? Have to make it easier for NEXT time.)

THANK YOU!

Jen
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Old 07-09-2008, 01:35 AM   #7
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Got it! ALL my lights work, inside and out, thanks to your help!

In the end here's what I had to do:
- swap the wires (regardless of color) on the taillights so they'd run dim for running lights, bright for signals and braking.

- run ground to each post on each marker light (8 total). The marker lights have two bulbs, 1 hot wire and no ground. As Frederick noted, they are apparently designed to attach to a metal body, so there is no ground wire. Still, kinda funny that EACH bulb in EACH marker had it's own ground, don't you think?

Thanks heaps for your help!

Jen
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Old 07-11-2008, 12:07 PM   #8
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Quote:
Got it! ALL my lights work, inside and out, thanks to your help!

Thanks heaps for your help!

Jen
Well, congratulations!

It seems like wiring is the one thing everybody does differently--and usually wrong.
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