have you stretched the wire or something from working in there? i had this a few years ago it was an old wire a little bit brittle and it snaped and streched inside the caseing, it also happend to my horn recently as you know, a new wire riged in and it was fine, but same thing it worked fine the day before then the next day it was dead lol, you can rig up the solenoid to the battery to test if that is working fine,