7701 Aurora Ave. N., Seattle, WA 98103 USA
phone: 206-297-3822 fax: 206-297-3828
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CONVERTING BETWEEN TWO-WIRE & ONE-WIRE HORNS
When attempting to hook up better horns, some owners find themselves faced with the seemingly impossible problem of hooking two wires up to a new horn that only provides for one. The difference is that single wire horns ground through their mounting bracket which must be securely attached to the frame in order to complete the circuit. That's the easy part. What's more involved is the difference in wiring needed to make them work.
The usual circuit for a two-wire horn has power from the fuse going into one terminal on the horn. Grounding the other terminal will cause the horn to sound. To control the circuit, the ground wire leads to the horn switch that, when activated, grounds the wire either to the handlebar or to another wire that is more positively grounded to the chassis somewhere.
To convert this circuit to operate one-wire horns requires the same relay used for the starter or to update the headlight circuit (19732500). Usually a horn relay can be mounted to the frame close to the horns so that very little additional wiring is necessary. The wire from the fuse that was connected to the original horn(s) now goes to terminals 30 and 86. Attach a new wire from terminal 87 to the one-wire horn(s). To terminal 85 goes the wire that grounds the relay through the handlebar switch. Terminal 87A isn't used.
Occasionally someone needs to revert back from one-wire horns to the dual-wire variety. In that case the relay can be removed and the lead that did go to either terminal 30 or 86 connected to one horn terminal. To the other terminal goes the wire to the handlebar switch. The switch grounds the wire which completes the circuit and sounds the horn. If two horns are to be used, the first is wired as described. The second is wired in series to the first: a short wire from each terminal of the first horn attaches to each terminal of the second in no particular order.
CHS HORN