I have a 1988 Ford F-150 Lariat XLT 5.0 and the old horns are singal terminal and the new horn is a double terminal
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1990 Ford F-150 Question: How do i install a dual terminal horn with single terminal wireing set up?
Answer #1patrick mannion from Greg Solow's Engine Room, February 21, 2012, 22:42Master
Single wire horns get power and the body of the horn is automatically grounded. It sounds like the horn you have gets one terminal connecting to the power wire that was going to the old horn, the second terminal on the new horn needs to have a ground wire attached to it connecting it to ground/metal on the body.