[JSeery]

Don't think the setup Tom posted will work. The ammeter has to be set up where all of the current going to and from the battery passes through it (one of the reasons they can be a safety issue, but that is another topic). It is looking at the direction the current is flowing to and from the battery. It needs to be connected between the main power wire from the battery to the rest of the system. When the lights are turned on for example, the current would be flowing from the battery to the lights with the ammeter in-between and would deflect toward the discharge side. If it was all connected up with the generator and VR and the vehicle was running (without the lights or other heavy loads turned on) the ammeter would deflect toward the charge side (current flowing toward the battery).

If you are wanting to use the car as a test rig, might try connecting a wire from the battery side of the starter solenoid. Remove the main power wire on the starter solenoid (normally the large yellow wire) that goes to the instrument panel. Connect that wire to the ammeter. Now connect a new wire from the ammeter back to the starter solenoid. Now try the headlight test and/or start the vehicle and check it out.

This puts the ammeter in the main current path to and from the battery and the ammeter will indicate current flow direction.