Connect pin #1 to the red shunt lead.
Connect pin #3 to the black shunt lead.
Use the large nuts on the shunt to connect to the charging circuit.
The shunt connects between the battery and alternator / load buss. Install the shunt with the red wire towards the alternator side.
A small amount of power ( 0-50 mv ) is dropped across the shunt. This power is sent to the instrument. The instrument is calibrated to receive this small voltage. Do not connect the instrument directly to battery power.
The shunt will show the current going into and out of the battery. If the charging circuit fails or the engine is not running the ammeter will show a neg charge when there is a draw on the battery.
Note! Do not run starter current through shunt. The starter draws hundreds of amps and the shunt will burn out, causing damage to the meter.