What trailer sway looks like

Question???
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if you manually use the trailer brake controller... will the brake lights light?
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factory or aftermarket..
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that is WITHOUT pressing on the TV brake petal.
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Yes, white bottles bouncing side to side on rear cargo rack....
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driver Froze... my opinion. Yes driver was steering ( Late ).. but Froze.
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many years ago... helping a friend move...
His Jeep CJ... with U-Haul 20 footer... Full. I was driving.
talk about the Tail wagging the dog... arrived safely..