Date: Sun, 6 May 2007 02:06:44 -0500
Reply-To: Matt Roberds <mattroberds@COX.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Matt Roberds <mattroberds@COX.NET>
Subject: Re: Help identifying part (image provided)
In-Reply-To: <20070506040311.JIVC22717.fed1rmmtai102.cox.net@fed1rmimpi04.cox.net>
Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed
> From: neil <musomuso@GMAIL.COM>
> Date: Sat, 5 May 2007 11:37:57 -0700
>
> http://web.mac.com/tubaneil/iWeb/Site%205/Mystery%20part.html
I know this part has already been identified and excised, but I figured
I'd add a little...
Most small trailers in the US and Canada have one lamp on each side that
serves as both the turn signal and brake lamp. Historically, most US
cars had a similar arrangement for their rear lamps, so hooking up
trailer lights was pretty simple - the left trailer lamp hooked to the
same wire as the left rear car lamp, and the right trailer lamp hooked
to the same wire as the right rear car lamp.
Most European and Japanese cars, as well as more recent US cars, have
two rear lamps on each side - one with a red lens for the brake lamp,
and one with a yellow (usually) or red (sometimes) lens for the turn
signal lamp. You've got two wires on each side of the car, but only
one wire on each side of the trailer. You can't just hook all three
wire ends together, because that would make the lamps on the car operate
incorrectly. Using two diodes would sort of work - the car lamps would
operate correctly, but the trailer lamps would only flash with the car
turn signals until you stepped on the brakes - then the trailer lamps
would come on solid no matter what the turn signals on the car were
doing.
That box does the magic to make the trailer lamps behave correctly when
connected to a car with separate rear turn and brake lamps. They come
in various flavors - some are a box with wires on both the "car" and
"trailer" ends; some have wires on the "car" end and a built-in
connector on the "trailer" end; some fancy ones have connectors to match
the factory wiring harness on the "car" end and a built-in connector on
the "trailer" end so they can be installed without any splicing at all.
The "trailer" end of the wiring is usually (not always!) four wires:
white (ground), brown (running lights), green (right turn/stop), and
yellow (left turn/stop). If you see a harness of white-brown-green-
yellow or brown-green-yellow wires hanging out near the rear bumper of a
car, it's quite often someone's attempt at a trailer wiring connection.
You can usually get 14 and 16 gauge four-wire "ribbon cable" (four
insulated wires bonded together) at the FLAPS.
The "car" end of the wiring varies more, but on the converter boxes, a
common configuration is five wires: white (ground), brown (running
lights), green (right turn only), yellow (left turn only), red (stop).
Some converter boxes omit the white (ground) wires on both the "car"
and "trailer" sides, so there are only four wires on the "car" side and
three on the "trailer" side.
Mini rant: The ground wire is NOT OPTIONAL! No, it won't ground through
the hitch ball - at least not after you hit the first bump! Both the
trailer and the car need ground wires. Even a wire that runs from the
trailer half of the connector to a sheet metal screw on the trailer
frame, and a wire that runs from the car half of the connector to a sheet
metal screw into the car body, is better than hoping it will ground
through the hitch ball. The Syncro Deluxe version is to make the ground
wire one or two gauges thicker than the other wires, and to replace the
sheet metal screw with a bolt, flat washer, ring terminal, toothed washer,
(car or trailer metal), flat washer, and self-locking nut in that order.
Hitch-ball grounding and/or broken ground wires are the leading cause of
flickering trailer lights. End of mini rant.
In general, one of the few things that will drive you crazier than DPO
stereo wiring is DPO trailer wiring. If you have a car, truck, or van
that's new to you and the outside lights are acting weird, run, don't
walk to the back of the car and inspect carefully for signs of trailer
wiring. This applies even if no sane person would attempt to tow a
trailer with that kind of vehicle (i.e., Geo Metro or similar). If
there are strange wires dangling around that are connected to the rear
lights, and you can't convince yourself that they are stock, get rid
of them. This can help your sanity immensely.
Matt Roberds
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