Posted by Paul on May 17, 1999 at 13:05:52:
In Reply to: Horn wiring? posted by stp on May 16, 1999 at 21:27:23:
{{I have an older very large dual trumpet horn that I would like to put on my truck. I need help with the wiring!!! I believe the horn are the vibrating type. There is one wire to each of the ends of the horns, which are pigtailed together. Then there is a type of relay box, approx 1"x2"x1", with three screw terminals.}} What you have is a horn relay. To check the horns just hook the wire to the positive terminal of your battery and then ground the body of the horn to the negative. The relay has three terminals for the horn switch, power supply, and power to the horn. You can get a new relay but if your horns are 6 volt, you must use a mechanical as an electronic relay won't work. 6 volt horns will work on a 12 volt system as long as you don't lay on them and hold it. You'll burn them out in continiuos use. Just a short honk though and they will last a long time. I had one on a car once and it would vibrate screws loose under the hood since they are getting twice the power they require.
To hook the relay up, you need to know which terminal is which. If one says "B" then a wire goes to the battery hot wire. Either a straight connection through a fuse or through the accessory switch in the ignition switch. It depends on whether you want the horn to work with the key off or not. I like using the key because it keeps kids from honking the horn while you're under the hood. The terminal marked "H" has a wire that goes to the horns. The horns ground out to the frame. The terminal marked "S" goes to the horn switch and then to ground.