I was just about to say charging too, then read the post by cossied, fix that and see where you get to.

but, you mechanic sounds a little dodgy mate, got a big spark with a spanner , should have disconnected the battery first really, then, he can't tell you what he shorted ??? Are you sure you want your cossie looked after by him ?

You say he's generous ... I reckon he's dangerous.