Are you sure that it is not just the relay that is clicking? If you have a volt meter you could check that you are actually getting 12v at the horn when you press the button.

 

I do have a voltage meter i will give that a try, and the sound definitely is coming from the horn, like its not get enough power and gives up instantly:dozey:

 

A relay is really a heavy duty switch that is controlled by another switch (the horn button in this case). Assuming that one side of your horn goes to ground then the other connection on the horn should go to one side of the normally open contacts of the relay. The other normally open contact of the relay should go to a good power source such as the +12v terminal of the battery, maybe via an inline fuse. This will ensure that the horn gets the amps required to make it work assuming that you have used decent wire that can handle the current. The energising coil of the relay should have one end going to ground, the other end is fed 12v from the horn button, when the button is pressed the coil gets 12v, it then closes the normally open contacts and feeds a heavy current 12v to the horn. Note that some bikes do things the opposite way round, they send a permanent 12v to the horn and the button just grounds out the other side of the horn. From memory on my 300 EXC they don't do it this way!

In either case a relay can be used to control the current going to the horn.

 

My horn isn't working good too. Nothing a few blue pills can't cure

Seriously, are you sure the horn itself is ok? Connect it directly to the battery so you can be sure it works...
If it just clatters its toast.

 

Dude the OP stated that it does work when he connects it across the battery. With regards to your medical condition it reminds me of a great forum signature that I saw once, maybe you could use it... "nerves of steel, heart of gold, knob of butter!"

 

Horn relay? That's a new one lol, unless it's some serious horn! Dodgy switch or wiring broken/breaking at the spade connector going to the horn I'd imagine.

 

I'm not an electrickery genious, but is it ac/dc issue?Where are you taking the supply from?
Direct from battery with inline switch and fuse should work DC.
But if youve tapped into the loom somewhere for supply, isnt that AC, so it won't work the same?
Or I'm talking shit? On bikes with no battery like XR600 you need supply off horn for GPS charger etc, as rest of system is AC.