Ok, so make some tests. With the engine running at a good fast idle, what is the voltage at the battery?
"Normal" is near 14V, a variance (depending on temperature) of 13.5--15 is OK
If it's low, make sure the belt is tight, and pull the green wire off the alternator. The exposed terminal on the alternator should be "battery" when key is in "run." Take a clip lead and ground this, start it up and easy bring up RPM. Ammeter should come up and with the engine running fast should peg the ammeter.
If it does, alternator is OK. If not, you have either a problem with the alternator OR the wiring.
If not, check voltage at the blue push-on terminal at the back, key on, engine off. Voltage should be close to same as battery voltage
If so, restart car with the other terminal still clipped to ground. Put one probe on ammeter output stud, other probe on battery positive. Bring up RPM to simulate "low cruise" and see what this voltage is. You are measuring the drop between the alternator output, through the bulkhead, the ammeter circuit, back out the bulkhead, and to the battery.
With the engine running at a "low cruise" condition, maybe a volt or so is all you should see here. If more, you have a wiring problem
One last thing to check is the ignition supply lead supplying the regulator. One lead to the regulator is green--goes to the alternator field. The other lead connects to your dark blue "ignition run" suppying the ignition system, the regulator, and the other field connection at the alternator. So the "non green" terminal at the regulator should ALSO be "same as battery" with the key in "run."
Otherwise, may be back to alternator --a blown diode or two, or bad stator winding, etc.
If that seems the case, best to find another alternator.
