Cruise control turns off when headlights turned on

My husband just added a trailer hitch to our 2007 Odyssey and did some wiring to plug in the trailer lights when needed. Now the cruise control cannot be set unless the headlights are turned off! I can see
that the cruise control is powered up. I turn off the headlights, then cruise control works normally, turn on headlights, and speed setting is cancelled. Guess I need to buy a manual with schematics, but does anyone know if these things are related?
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Somewhere in the trailer harness he's getting "feedback" from the trailer lights through the ground line for the brakes. With the headlights on, that closing of the ground line is looking to the car like your foot is on the brakes thus cancelling the cruise control.
I would first suspect he used an improper aftermarket trailer harness that lacks the proper isolation.
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Sara wrote:

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I think Seth described it perfectly. He should have installed a module that 'adapts' the Honda connector to work with whatever style of trailer you use.
http://www.hondasuv.com/members/showthread.php?t !073& http://www.hondasuv.com/members/showthread.php?t 685&
Look through these threads and follow any links provided. You can also sign in and _SEARCH_. No need to ask, the answers are already there.
'Curly'
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