Cobra trailers have a seven wire plug. Most glider pilots in the USA use the flat four wire connectors at the back of the tow vehicle.The cobra plug has all of the pins labeled, but the trick is to associate the correct pin on the cobra plug with the flat four wire plug on the back of your car.
First, here is what the USA flat four wire plug has --
Ground = White
Left Turn = Yellow
Right Turn = Green
Tail lights = BrownThe plug on the cobra trailer has seven pins --
Pin # 7 is in the center
Pin # 1 is labeled 1LOn the inside of the plug, you will see the labels embossed on the plug. The first character of each label is the pin number. Here is what they are labeled, from Pins from one to seven, and where they should connect to onthe flat USA four wire plug.
Cobra Label Pin Number Function Flat 4 wire - USA 1L 1 Left Turn Yellow 2/54G 2 ? 3/31 3 Ground White 4R 4 Right Turn Green 5/58R 5 Tail + side lights Brown 654 6 ? 7/58L 7 Tail + side lights Brown The tail light covers are half red and half orange. You must also remove the lens from each of the tail lights, turn them upside down, so that you have mostly red illuminated when you use the brakes.
Using this conversion method, the brake lights come on OK, but there are some problems.
An alternate method is to wire in the following manner:
This info was provided to me by Mike, but rather placing any responsibility on him, I won't mention his last name. Mike's explaination seems quite simple and doable. Let me know if it works for you.
Here is the Cobra wiring info. The plug has seven pins, six arranged in
a circle with the seventh in the center. The pins are labeled one
through
seven.Pin 1: left turn
Pin 2: license plate light
Pin 3: ground
Pin 4: right turn
Pin 5: right running light
Pin 6: stop light
Pin 7: left running light
If your automobile has a five wire harness (some foreign cars) then
the wiring is easy. The five wires are left turn, right turn, stop,
ground, and running. So pins 2, 5 and 7 are wired together and the
others as you expect.American cars mostly have a four wire harness. Things are more
interesting in this case. You need to go to radio shack and buy
two diodes (about $1.00 each) with about a 2amp rating at anything
from 50volts to 250volts. These are common and easy to find.The four wires on the car are ground, left turn, right turn and
running. There is no separate stop wire. Here is what you do:connect car ground to pin 3 (trailer ground).
connect car left turn to pin 1 (trailer left turn).
connect car right turn to pin 4 (trailer right turn).
connect car running to pins 2, 5 and 7 (trailer license and running).
Finally, you connect car left turn through the diode to pin 6 (trailer
stop).
And, also, you connect car right turn through the second diode to pin 6
again.What this does is to allow either the car's left or right turn wire to
power the trailer's stop light. The diodes avoid a short that you would
have if you wired them directly together to pin 6.Remember, diodes are one-way devices. If you wire them up in the
incorrect orientation, the trailer stop light will not work. Rewire it the other
way.If you do this, the trailer lights will work *almost* correctly, but
not perfectly. The problem is that when you brake both the trailers
brake lights and the trailers turn lights will both go on. Annoying,
but I have driven my trailer more than 3000 miles this way and nobody
complained.To fix this problem, you need a much more complicated circuit. If you
check in a trailer supply store, you may be able to buy a small box
that does the correct conversion. But be careful, most trailer shops
sell a box, but it doesn't do the right thing with a cobra trailer.
Most boxes convert a five wire car to a four wire trailer and NOT
the other way around.Also, have a few spare fuses for your car handy. You may need them
while you are getting things right.
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