You've got your wires hooked up incorrectly... obviously!

Open up your relay, you'll see a coil of wire, and a larger gauge tab which goes above the coil.

The wire coming from the horn button/actuator should go into one side of the coil, and back out to ground. This low current will in turn create a magnetic field which pulls the top tab down and completes the circuit for the "high" current side which is your horn. You'll have 12v going into the tab and the horn attached to the other side.

I know thats a horrible description, but, if you open up the realy, you'll see what I mean.

Sounds like you have the horn button connected to the relay correctly, but, have put in the ignition wire into the equation somewhere.

Take a picture of the relay with the cap off, and of the connections on the bottom and I'll tell you where to put your wires...if you want.

 

Now something freaky's happening.

Sometimes it works. Sometimes it doesn't.

Half the time my horn works as it should, and half the time it starts the car/grinds the starter.

It seems like if I start the car with the horn working as the horn (it doesn't start the car, and it makes noise when I press it) then it will keep being normal until I turn the car off/magic things happen.

And vice/versa.

Also, when my horn is somehow randomly magically connected to the starter, my cruise control doesn't work.

I'll figure it out eventually........

 

It shouldn't be that difficult. This is a pretty major issue you have, and can be easily fixed... Post a picture of the relay or just get your wiring correct.

 

oh wow...

I'd have to see it in person to know what is happening.

 

is this figured out yet?