Ammeter in instrument cluster short-circuit

I removed the instrument cluster on my dart swinger, from 1972. When I put it all back the ammeterconnections on the back of the instrument cluster sparks. The only thing I've done differently is to use a 72ah battery instead of a 56ah (as the 56ah is completely dead).
The battery sparks to.
Does anyone have an idea of what's going on? Is the battery too powerful?

I'm very sure I've put the cables to the ammeter in the right place. One going from the fusebox and one coming from the ballast in the engine bay. However, just to be sure, does anyone care to share which one goes where on the backside of the instrument cluster?

I have tried to switch places of the cables without success. Can the ammeter be broken and therefore short-circuit?

This is my first classic car and I wasn't expecting this problem when all I wanted to do was to install a new speedometer cable....