Cruiser
Posts: 208
Wichita, Kansas | I have been asked why another relay is required when hooking up a high power horn, when the Vision already has a relay labeled "horn relay". (All information below is taken from the Vision Wiring Diagram, page 510, included in the service manual.) What it does have is a horn enable (or circuit isolation) relay which will remove power from the horn when the ignition switch is in the OFF position. The horn itself is controlled directly by the horn switch on the handlebars. What this means is that if you hook up your high power horn directly in place of the OEM horn, it will chew up your horn switch contacts like my granddaughter going through a cookie. It also turns off the one or two optional Powerlets which are sometimes mounted on the center console for heated clothing or other accessories. For those who care, the logic follows.
Starting at the horn relay in the bottom center of the diagram, there is a 303 series relay with normally open contacts. That means no power can flow through the relay until it is activated. The activating coil has two wires. The black (pin 85) connects to ground and the pink (pin 86) connects to the ignition switch. Therefore the coil receives power when the switch is ON. That pulls the relay contacts shut, closing the connection between pins 30 and 87. The grey wire (pin 30) connects to a 20 Amp fuse which is connected directly to the battery. When the relay is activated, the closed contacts apply the power from the fuse to the grey/pink wire (pin 87).
The grey/pink wire then goes up to a junction, turns left and goes through a connector to the horn switch. When this switch is closed, power is applied to the horn (left center) via the grey wire. The other side of the horn is always connected to ground through a black wire, so now the horn will sound. In short, the switch controls the horn directly and the "horn relay" only keeps it off when the ignition is off.
The horn switch can be used to control another relay to safely power a high power horn, such as the Stebel.
Powerlets: If you follow the grey/pink wire on the wiring diagram up from that junction where it goes to the horn button, it goes up and over to the two powerlets in the top center of the page. Thus, the horn relay turns off the auxiliary Powerlets when the ignition is off. These are the two optional Powerlets which can be mounted on the center console. There are two connectors there, which conveniently accept ΒΌ"' flag terminals making this a handy place to draw power for accessories, such as the horn relay I just added for the Stebel, or any other accessory as long as you stay at less than 20 Amps total.
Edited by KansasGuardsman 2009-01-11 9:35 PM
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Vision Horn Relay Logic
