Join Date: Aug 2011
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1) I assure you no plant. I have a detailed write-up and in my initial post, I offered it to anyone who asks. (My purpose in posting was not to illuminate what I think is an unusual problem that I hope few would ever experience, but rather to broadcast the availability of a resource that I found head and shoulders above the others, that saved the day for me, and that others could resort to for whatever problems they might encounter. If I had gone to this guy first, rather than eight days later, I'd have saved myself a lot of hot, sweaty work, a not insignificant expense with no results, and a good deal of angst about ever getting my boat fixed.)
2) If you want to make an exercise out of it, here goes:
A) Assume a system that has been installed and working just fine for years, capable of restoring about 80+ AH of a 100 AH discharge from a day or so on the hook, in 60 minutes of engine running at 1700 RPM.
B) All of a sudden you notice that, shortly after starting engine and setting revs for 1400-1500, the tach reading drops to about 900-1000 and stays there, regardless of changes in engine RPM.
C) Next time you have big nick on the batteries, you notice that concurrent with tach drop, the alternator is putting out much less current and voltage than it should. Getting from "bulk" mode to "acceptance" mode takes way too long. However, once it gets to "acceptance," tach function resumes normal.
D) Problem grows worse; now alternator output so low that regulator will never get to "acceptance."
Pause here for first round of answers.
E) Since you have a spare regulator wired in, you switch to the spare regulator. No improvement.
F) You also have spare alternator, so you do alternator swap. No improvement.
G) Flailing around, you lift, inspect, polish, restore and torque all wire terminations, big and little. (We do this every year or so anyhow, so no surprise that they are all clean.) No improvement.
H) Really flailing around, you have the batteries (which aren't very old East Penn gels and which respond to shore-power based charging via Heart Interface as normal) tested, and you take not one, but both alternators to not one, but two qualified alternator shops for complete inspection and testing. All tests show batteries and alternators just fine. Problem persists.
I) At this point, you decide you're not as smart as you thought you were, so you bring in local marine systems outfit with great reputation. They come on board, find nothing amiss but can't solve the problem, and leave reporting selves "stumped."
J) So at this point you decide to perform the always attention-getting "full field" test: everything off, disconnect regulator from alternator, make up a #12 lead with insulated spade on one end and alligator clip on the other, attach spade to field terminal of alternator, start engine and let it settle, and clip alligator to B+ terminal of one battery. Big sparks. No improvement.
OK, who has figured it out?
Last edited by Prescinding; 08-04-2011 at 05:13 PM.