Civic EG

so im in the process of hooking up my horn on an aftermarket detachable steering wheel. I looked at a DIY saying u unplug the 4 pin harness that plugs to the horn relay and find the constant 12v. i checked it one day i had 12v( i had the Horn unplugged). but then i went to check another day and i got nothing when i had my horn plugged in.

Any one know why this is happening? im gonna check again later see if i got 12v again.

nevermind i found out my fuse got blown. i needa kno what caused it. was it my horn? i got the horn from the junkyard out of the same car, doesnt kno if it works or not though