to test alt. remove regulator
field wire from alt. connect alt field post to 12v. it will put out full amps. don't leave it on for long. if alt is not putting out full amps, probably is alt.
with regulator on. test voltage of battery
sense wire, and field voltage. if battery
is low and needs charging, feild voltage should be ~12v. if batteries are full it will be under 6v or so. basicily the reg changes the field voltage to adjust how much it charges. if batteries are low and field voltage is low, then reg is not driving the alt properly. or sensing wrong voltage.
the battery and alt temp readings scroll on the screen
and you can read them. same with battery voltage and voltage it's trying to hit. BV and CV.
IE if BV is 12.5v and CV is 14.4v and field voltage is 6v something is wrong. as it should be trying to hit 14.4v and driving the field voltage higher.