Twin 12v Italian chrome and black wind tone horns (Pair)
How to connect a 4-pin relay
1. If you have 2 wires going to your present horn(s).
(a) Connect these wires to pins 86 and 87 respectively.
(b) Check to see which of the (original) wires is "live" by using by using a tester or, if you do not have one, a 12 volt bulb. The bulb will illuminate when connected with the live wire and the car body (earth)
(c) Connect the "live" pin with pin 30. If the horns don't turn off when the button is released, you have connected the "non live" pin to 30.
(d) Connect pin 87 to the new first horn and then connect this to the second new horn. The new horns have to be bolted to the body of the car and a good electrical connection through this (bolt point) should exist.
(e) Try the horns.
2. If you have 1 wire going to your present horn(s).
(a) Simply connect this one wire to the new horn and connect the second horn as (d) above. You do not need the relay.
(b) If you want to use the relay, proceed as above, a to e, but connect 85 to earth ( i.e. the bodywork)
Finally, have a look at: http://www.autoshop101.com/forms/hweb2.pdf