Re: Alternator stopped working

Bill Kinney


I am not very familiar with the wiring of a Maramu, but I am guessing these are both 12V alternators feeding a 12V battery bank?

Is this the original engine?
How long have they not been working?
Did they both die at the same time?  While the engine was running?  
Can you describe how you did the measurements you are making that tell you the "output voltage" and the "voltage supply"?
On the alternator with the external regulator, can you measure the Field voltage coming from the regulator?  (Usually the terminal will be labeled F, or FLD, or DF, or EXE, or 67)

If you are measuring across the B+ and B- terminals of the alternators and you get very low readings that are DIFFERENT from each other, that strongly suggests they are disconnected from the batteries.  A loose connection?  Or maybe a common fuse? Are there any other electrical problems you notice?

If that is the issue, you might have bigger problems.  Running an alternator that is not connected to a battery can destroy the diodes.  

There might be a lot going on here, especially when you say your batteries are "busted." How bad are they?  It is also difficult ot be sure especially on an older boat where many wiring changes could have been done by previous owners of varying degrees of skill.

Bill Kinney
SM160, Harmonie
Port Louis, Grenada

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