Trouble with Trailer Lights - Defender Source
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  #1  
Old July 7th, 2008, 09:24 PM
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Douglas Wozny
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Trouble with Trailer Lights

Have a 94 D90 with Land Rover trailer light plug and adaptor to use my flat 4 trailer plug. Checked adaptor with test light and all worked correctly. Plugged in trailer and things went goofy. First thing I noticed was D90 backup light came when any of the other lights came on. Both turn signal lights on trailer blink very dimly when either the right or left turn signal was activated. Running lights on trailer very dim when lights of D90 truned on. Brake lights seem to work OK except D90 backup light comes on.

Any Ideas?
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  #2  
Old July 7th, 2008, 09:35 PM
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Andrew Najarian
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Well, if it tested alright with at the back of the car, you might find the problem is a short in the trailer wiring, especially if this is a boat/pwc trailer that is being submerged in water frequently. I would clean up the connections and check the trailer lights for corrosion inside of them. Do you have another vehicle you can connect the trailer to to see if it acts the same way?
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  #3  
Old July 8th, 2008, 08:20 AM
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Douglas Wozny
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The trailer lights work OK when hooked up to my '74 CJ5 and my neighbor's car.
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  #4  
Old July 8th, 2008, 05:08 PM
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Check the ground wire. I forget where it is on a 1994, but that was my issue when I had the same problem. IIRC I just grounded the wire directly to a cage bolt.
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Old July 8th, 2008, 09:03 PM
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Douglas Wozny
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Evilfij,

What ground wire I am to check? The one on the vehicle's trailer light plug or the main vehicle ground?

If the ground is bad, why does the test light work? Just can't figure out why plugging the trailer in makes things go goofy.
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  #6  
Old July 8th, 2008, 10:47 PM
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I would suspect a ground issue with the 7 pin socket if the back up light comes on when the brakes are applied- but only when the trailer wiring is pluged in, since the 4 prong adapter has nothing to do with the back up light. Or possibly a short in the adapter.
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  #7  
Old September 21st, 2008, 05:55 PM
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Douglas Wozny
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Finially got up the courage and found time to look behind the rear passenger side speaker where the "box" for the trailer connector is located. Going out of the "box" there are four wires: white(ground), brown (tail/parking), green (right turn/brake) and yellow (left turn/brake). Wires going into the "box" are white, yellow, black and green. The white is connected to 2 green/brown wires. The black is connected to 2 red/black wires. The yellow is connected to 2 red/green wires. The green is connected to 3 wires: a large gauge green/purple wire, a small gauge green/purple wire and a red wire. Not sure what the "box" does as four wires go in and four wires come out but I guess it does something.

Evilfij and Maryland 110 talk about grounding issues. Can anyone elaborate on that. From what I can see everthing is fine except when I plug in the trailer. And the trailer look fine with other vehicles. It is a simple circuit. It is not like I am working on a super collidor. HELP!
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  #8  
Old September 22nd, 2008, 03:43 PM
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The box is most likely a converter to go from the rover set up with a separate brake light and turn signal light to the trailer which uses the same bulb for brakes and turn signal.

As for the ground comment, that is most often the problem, I've had with trailer wiring. They sit for long periods of time and quite often the ground connections at the tail lights etc get corroded. I would suggest you start at the back end of the trailer and check every ground connection. You said it worked with other vehicles. If you're sure of that, and it is recent, then I would check the ground connection between the trailer and the tow vehicle. As a last resort, it may be the little black box, however, I don't think I've ever had one go bad on me.
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  #9  
Old September 22nd, 2008, 07:54 PM
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Loic Fabro
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Quote:
Originally Posted by slorocco
The box is most likely a converter to go from the rover set up with a separate brake light and turn signal light to the trailer which uses the same bulb for brakes and turn signal.
What you really mean is "Euro style" to "US Style" wiring!
The old Euro trailer plug had 7 pins (the new standard is 13 pins).
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