The basic idea behind the horn relay is power is always applied to the relay coil and to one side of the NO switch. When the horn button is pressed, this grounds the relay coil which in turn pulls the relay wiper and connects the two relay poles (causing the click noise). The power to the horn does not pass through horn button. It is direct from the source through the relay contacts to the horn itself, then to ground.
If you would like a diagram I can draw one up.
Dale
When I die, I want to go peacefully like my Grandfather did, in his sleep -- not screaming, like the passengers in his car.
-Unknown-
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