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Author Topic:   Trailer Wiring
17 bodega posted 06-18-2006 02:56 AM ET (US)   Profile for 17 bodega   Send Email to 17 bodega  
Two tailights were badly corroded and needed replacement. I bought new tailights, but they don't have a ground wire that grounds to the chassis like the old lights. After connecting the wires according to the instructions, the right tail light does not light, but the right blinker and brake light work fine. All other lights on the trailer seem fine. The right bulbs are good. What would cause only the right tail lamp to fail to light?


jechura posted 06-18-2006 07:55 AM ET (US)     Profile for jechura  Send Email to jechura     
Somewhere on your trailer the one wire that powers the tail lamps is split to go to both sides. From that split to the bulb is the problem. Check at your tail light with a 12 volt tester to see if there is power in the wire where you made the connection. If there is power it's the new taillight. No power it's in the wiring.


jimh posted 06-18-2006 08:53 AM ET (US)     Profile for jimh  Send Email to jimh     
You did not mention the trailer wiring arrangement. We assume you have the common "flat four" arrangement. The standard wiring color code is as follows:


WHITE = battery negative or trailer chassis ground

BROWN = tail lights and clearance lights

YELLOW = left turn light and left brake light

GREEN = right turn light and right brake light

To help remember the color code:

RIGHT and GREEN both have an "R".
YELLOW and LEFT both have an "L"
WHITE is the neutral color
BROWN is burning all the time

If the lamp for your right tail light does not illuminate:

--it is not receiving current from the BROWN conductor, or

--it is not returning current to the WHITE conductor, or

--there is a problem with the light bulb or its socket in the lamp

Here is a good article from the fine folks at TRAILER BOAT MAGAZINE on diagnoses and repair of trailer lighting problems:

17 bodega posted 06-18-2006 12:37 PM ET (US)     Profile for 17 bodega  Send Email to 17 bodega     
Thanks for that info. It is the flat four wiring system in my EZ LOADER. Based on your responses, I should be able to correct the problem.

I'm guessing the brown on the right tail lamp is the problem.

17 bodega posted 06-18-2006 02:09 PM ET (US)     Profile for 17 bodega  Send Email to 17 bodega     
problem fixed. it was the brown wire and the culprit was a poor plug connector. My gripe about "WESBAR" and "EZ LOADER" is that I would expect better corrosion resistant connectors so the tailights can be easily removed and replaced. This is actually true, but the connectors behind those went bad and then there are no replacements available other than the ANCHOR connectors you crimp yourself.

Thanks again Jim and Jerry for the tips on wire colors... I'm back on the road with all lights firing.


17 bodega posted 06-18-2006 02:13 PM ET (US)     Profile for 17 bodega  Send Email to 17 bodega     
Another thing I notice when stripping the wires on these connecions is the wire appears burnt and charred, with charcoal residue, as if the wire has suffered a short or overheating. I notice this often with boat wiring even in cases where there has been no short on the wires. What gives?

Thanks for all the electrical help from the forum lately. As I resore my old boat to full operating condition, it seems my latest adventures have been in the 12 volt wiring systems of my car, boat and trailer.

Happy Fathers Day to all the Dads out there!


Chuck Tribolet posted 06-18-2006 07:56 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
The copper wire looks burnt and charred? Or the "rubber"
insulation looks burnt and charred?

If it's just the wire, it's not burnt and charred, it just
has a coating of some stuff that happens when it gets wet
with salt water. If it's not too bad, you can sand the
strands with 1000 grit emery paper and take the black off.
If the copper is crumbly, it's "wire cancer" and you have
to replace the wire.

If it's the insulation, it probably got too hot due to a
high load or a short.


17 bodega posted 06-19-2006 01:26 AM ET (US)     Profile for 17 bodega  Send Email to 17 bodega     

It's the copper. It looks kind of blackish and it does appear more brittle than before. All the new wire I use is the corrosion resistant wire, which seems to hold up much better and has less tendency to turn color.

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