Need help.
Have an old S3290CDi W220 2001.
Been having battery drainage problems for a long time.
After many different possibilities I was directed to the alternator, took it off eventually very messy and needed to remove the waterpump.
Checked the alternator the diode seems to be working, but it is producing AC current of approx 3V AC.
How or what is the best way of testing an alternator?

 

Could it be the Regulator, and how do you check that?

 

Most large auto parts stores have a test rig, and will test the alternator at no cost.

 

Thank everyone.

 

this guy is not getting it:
What was his solution to the problem we were trying to help him with ???