Join Date: Sep 2001
Location: Temple City, Ca
"'m sorry for this long read but I really don't understand how this all works. What is the horn relay for, why is it there"
Because the horn takes a large amount of current to operate, it is better to switch it with a relay instead of a switch.
1, If the horn button (a switch) was the only think that switched the horn, the horn button switch would require very large contacts to operate.
2, If the horn button (a switch) was the only think that switched the horn, the wires to the horn button switch would have to be the size of the large green wire to operate.
3, It is safer to switch ground, on the horn button, than a large current 12 volt line.
4, It's easier to run small wire up the column instead of a larger gage wire.
Using a relay makes good sense for the application.
"and how does it work?"
It works by running the large current load through the contacts of the relay. Relay unenergized, the contacts are open-no horn sound. Relay energized, the contacts close-horn blows. Applying power to the relay coil closes the relay. The coil needs 12 volts on one end and ground on the other end to close the relay. One side, the 12 volt side, is tied to the terminal where the red wire goes. This side of the coil always has 12 volts on it. The other side of the coil is the black wire that goes to the horn button. When you push on the horn button, the button grounds the black wire. When the black wire is grounded, the coil gets grounded, coil is energized, closes the relay contacts, makes the horn work.
Bottom line, you need two things to make the relay close. Without the horn attached it makes a slight "click" sound. You need the red wire with 12 volts. You need to ground the terminal where the horn button black wire goes to. Any clean spot on the frame will work. This is the same as pushing the horn button.
The relay red wire is also attached (inside) to one of the relay contacts. When the relay "clicks" and closes, 12 volts from the red wire goes through the relay contacts and out the green wire.
The voltage regulator has nothing to do with the horn.