trailer wiring

[DarrellC]

So, I rewired my utility trailer. white to ground. Brown to tail lights and side marker. Green to right and yellow to left. The only thing that works is the tail lamps and side lights. What did I do wrong?

[TDKPE]

So far, it sounds like you did nothing wrong. Did the system work with the tow vehicle before you rewired? Modern cars have a little brain unit in the wiring to convert from separate turn and stop lights to the North American standard of combined lighting (I think European trailers have separate amber turn signals), which may be having a problem. If it exists. I would start by checking the health of the stop/turn pins on the vehicle, either with a voltmeter, or with one of those little trailer connection testers.

And do you know for sure that the brighter elements of the stop/turn/tail lights even work?

[DarrellC]

yes, it worked before, but I rewired with a new kit. new tail lamps and wiring. Had used it with this tow vehicle before. Has factory 4 pin flat and 7 pin round. Tow an RV with the round plug and it works fine. if I wired the tail lamps wrong, could this be the problem.

[TDKPE]

DarrellC said:

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Has factory 4 pin flat and 7 pin round. Tow an RV with the round plug and it works fine. if I wired the tail lamps wrong, could this be the problem.

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Since you haven't used the 4-flat connection in the past, that's where I'd start. The connection to those two pins in the socket is untested, though the circuitry that combines the stop and turn lights into one (on each side), if it exists (depends on how the tow vehicle is wired), seems to be working if the 7-blade round connection works.

And leave open the possibility that the lights themselves are defective. If they're LED, then there's some circuitry in the light units themselves to combine the tail and stop/turn to make the same diodes brighter, rather than the independent filaments of a bulb.

[daddo]

Get a known source of 12+ at the plug (brown wire) and jump it to the yellow then brown wire. If the lights fail, the problem is beyond the plug.

Without seeing what you have connected it is difficult to know exactly where to look.

What type lights? LED or 1154/1157's?

[DarrellC]

not LED

[TDKPE]

DarrellC said:

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not LED

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Could be wrong bulbs (single-filament), or in the wrong way, or not all the way in, or defective units.

What daddo said; try a known +12V. Maybe through the old plug, if you still have it. Or test leads with alligator clips. Or just wire.

Comes a point where you may need to separate the lights and put power to them, one filament at a time.

Oh, and if you're using those quick-splice (or snap-lock) connectors, they don't always make a good connection, and they don't always last very long when they do.

Could even be a blown fuse in the car somewhere, especially if running and stop/turn are on different fuses. One reason for checking for voltage at those pins.

[DarrellC]

probably dumb question, but what do I use for a "known 12 volt source"? will a battery charger woek?

[TDKPE]

Charger voltage may be too high, with no load on it. Since you have an RV, use the #4 pin (aux +12V), or turn on the running lights and use the brown lead on the 4-flat or the #3 on the 7-way. Plus ground, of course.

[Snipe Hunter]

Something I learned about trailer wiring.... pay particularly close attention to your ground.

I can't tell you how many times I fixed or witness repairs to faulty trailer wiring by re-connecting the ground wires(s).

I bought a boat in Conn and had to trailer it back to Md. The seller told me the lights didn't work before I made the trip. I took crimpers and connectors with me and in a couple minutes I fixed the lights. Exposed wiring connections sitting out in the elements don't hold up well and most trailer wiring and lighting is made about as cheaply as possible.