trailer light problems


Old 10-15-09, 07:37 AM
Thread Starter
Join Date: Oct 2009
Location: Iowa
Posts: 1
trailer light problems

Installed all new wiring and lights on horse trailer. Used 4 wire flat harness. Old trailer so I wired brand new wire from each tail light mounting bolt to trailer ground. Tow vehicle is 2002 Silverado with the factory installed towing package. Has the built in 7 wire round connector. Used a 7 way-to-4 way adapter, between vehicle and trailer. Brake lights work. Tail lights work. both signals work. BUT if I hold brake pedal down AND turn on either turn signal, both lights blink on the trailer. Same with tails. Turn on headlights AND turn signal, and both lights blink. Help! Thanks!

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Old 10-15-09, 09:27 AM
Join Date: Aug 2006
Location: santa fe /texas
Posts: 998
i do not know the soloution.
but the problem is('I' think) that the tow vehicle uses a separate bulb for the turn signal and the brake lite.
the trailer uses one bulb for both.
Old 10-15-09, 10:22 AM
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Join Date: Oct 2002
Location: Hamilton County, Ohio
Posts: 4,292
newtofta is on the right track. If you have separate bulbs on the truck for turn and stop - usually red and yellow, then you will need a converter . They convert the three filament system on the truck (stop - turn - tail) to the two filament system on the trailer (stop & turn on one and tail on the other).
Any store that handles trailer parts and accessories should be able to help you. Some are plug and play, and some need to be hand wired to the trucks wiring.
Old 10-15-09, 10:47 AM
Join Date: Jan 2007
Location: North Central Indiana
Posts: 912
trailer lights

Havent tangled with any two light vehicles but I would think if the plug was there this would be addressed. I would think in terms of lack of ground,the thing that most overlook.
Old 10-15-09, 11:51 PM
Join Date: Jul 2005
Location: usa
Posts: 33
The previous post is spot on. power looks to get to ground by the path of lest resistance. if that is through other filaments then so be it. an 02 silverado should already be wired for a brake/tail combo. Unless someone changed it.
Old 10-16-09, 05:42 AM
Join Date: May 2006
Location: Iowa!!!!!
Posts: 3,769
Back on Goldstar's post - the third brake light (the three bulb system) is what causes the problem and you'll need the converter to run out of the factory wiring.

Or you can hand wire from each side of the truck - each bulb for turn signals and come off one brake bulb for the brake lights on the trailer.

I would get the converter.

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