Wrong Alternator?

Since you are willing to take it apart, might as well try to figure out what is wrong. Then you can replace whatever is needed and you'll have a good backup.
That's the Royal You. LOL It might be someone you pay to replace the part.

A. Remove the ground brush. Measure resistance between the positive terminal to ground.
There should be no continuity. In other words, infinate resistance.

B. Stick the probe to the slip ring, or take the case apart and check for continuity between the slip rings.
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There should be very little resistance in the rotor windings. If its open, its definately no good. Otherwise its a maybe. It could have two of the three windings open. That would still show coninuity on a meter but 2/3 of the electromagnetic would be dead.


Bench checking the stator and rectifier is more difficult.
If the multimeter has a diode tester you can try to check them.
The complication is they are soldered together in sets of 3 positive and three negative.
There is a special tester but hard to find...
That's all of the easy benchtop tests I can think of off the top of my head.