If you have installled LED lights (stop lights, turn signal trafficator lights etc.), the LEDs will draw very little current, so, there will be very little movement of the ammeter which measures that small current. To test your ammeter, put in an incandescent 1156 bulb in you tail/stop light socket. Then, with the key on, activate the brake light, this should cause the ammeter to deflect 5 to 10 degrees of arc.