It's like when someone calls into CarTalk, and they spend ten minutes trying to carefully diagnose the issue, and they keep throwing out theories, and then one of them says, "yeah, but if that were the case, his check engine light would be on", and the guy goes, "oh, my check engine light *is* on!"...

*sigh*

In other words... that's something you should have told us right from the beginning.

Yes, tying the accessory lines together could easily blow a fuse or fry something. Thats a +12v line being attached to another +12v line. It wasn't meant to be hooked up that way. The thing that you were trying to do there requires a special kind of autoswitching box such as the Sony XA-39II instead.

Click on the word "Repairs" at the top of this page, and get it on its way to Stu at Eutronix.