This morning the horn wouldn't sound when I went to pip the kids... It has worked fine since I got it and just now none of the 3 buttons work at all. I checked the horn fuse - not blown; I took the horn sounder mounted in front of the battery out and checked the terminals and tested it on a 12V transformer - it sounded (quite loudly actually ) so I am not sure how to begin further diagnosis. I assume since it is not one button it is in the wiring and not sure if the horn should sound when the key is out (never tried it) How do I sus this out - use a multimeter on the wires etc??