First determine if the CIRCUIT PATH from the alternator to the battery has a problem
First, check that the belt is tight!!!!
Next, run the engine at fast idle. With all accessories off, measure voltage at battery terminals and then at the alternator output stud. If the output stud is "way high" say 16V or higher, then you have a problem in that charge path to the battery.
If the alternator stud is fairly low, below 13.5, "it is not charging"
If this last is the case, determine if either alternator works.
With your field jumper to ground, and the engine off, run a jumper from the insulated field connection direct to battery. The starter relay stud is a good place. When you hook this up in subdued light, you should be able to detect a small spark.
Run the engine and watch the ammeter. The ammeter should come up into "charge" higher as you bring up RPM. If not, with engine running, and with the field jumpered to battery, AGAIN compare battery voltage to alternator stud voltage at "fast idle". If the alternator stud is low, down around 13 or less, the alternator is not charging.
If the above test DOES show a charge, now check the field wiring for the regulator. Hook everything up "normal," and then disconnect the VR wires. Jumper them together. Repeat your test as above, IE run engine look at ammeter. If you show a good charge......replace the VR
Make SURE the VR is grounded.
