Wow, DC clamp ammeters have gotten cheap
But still, a $20 multimeter can pretty much do the job just as well. If the alternator is not putting out 14.4 volts, or at least 13.8 at idle, it isn't going to be charging. Odds are if it is putting out the correct voltage, it will be putting out as much amperage as it is capable of--or as the regulator
thinks it should.
If the alternator is putting out but the battery
failing to hold the charge, the batteries are shot. If the alternator isn't putting out voltage, the alternator/regulator is shot. (Rashly assuming the belt, installation
, connections, simple mechanical things are all right.)