Um...find a new mechanic. This guy is a joker. The fuse is there to protect the electrical system. When you put a wire in there like he did this effectively removes the fuse safeguard. I would have to say that you are lucky you didn't have a more serious melt-down or even an electrical fire. When wires short with enough current running through them they light up like toaster wires melting all insulation and anything else they happen to be in contact with. Heh, 2nd mistake is letting your ex take your wheels. Now your Cam is pissed off.

Did your speedo stop working after the mechanic pulled his wire trick? If so I would bet that the electrical system has been damaged from this. You need to talk to these fools. They need to either fix the problem correctly or pay the bill to have it fixed right. Tough situation. I would talk to the shop manager or better yet the owner.