Whats the difference between an Amp gauge in a volt gauge?

A volt gauge will tell you the charge state of the electrical system by just turning on the key, Amp gauge only works if its running or how much current draw there is.

Why is an ammeter connected in series in a circuit?

In order for an ammeter to measure a devices current, it must be connected in series to that device. This is necessary because objects in series experience the same current. Ammeter in Series: An ammeter (A) is placed in series to measure current. All of the current in this circuit flows through the meter.