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[waughoo]

I was out for my first test run after a VERY long time at the dock and all was working fine until I noticed erratic movements from the tach needle.  It then started to pulse rhythmically and eventually went to zero, I then noticed that the volt meter was showing resting voltage.

Belt was fine, and none of the wiring looked out of order.  My question revolves around if this is just an end of life failure or if there is something else at foot that I should look into.

Anyone have any input?

[mark_53]

blown fuse from alt to battery?

[waughoo]

I had thought of that as it acted as if it lost its load to dump to.  I havent gotten to that step of adding fuses to all the wires so that isn't the case.  That said, I haven't check the line from alternator to battery yet.

[Ron Hill]

Alex : Check all of the alternator wiring connections!!

A thought

[Patches]

What Ron said.

Also, check the ground to the starter solenoid bolt.  I had similar symptoms and discovered that bolt had backed out giving erratic readings on the tach.

Patches

[waughoo]

All good suggestions.  We were out today and the tach jumped a bit at start up and then nothing while underway and then reappeared at idle as we entered the marina.  This makes me wonder if it is connection based.  You could also hear the engine load up intermittantly indicating the alternator field was being excited.

[ewengstrom]

This is going to sound odd...but I had pretty much the same thing happen two weeks ago on the second day out on a 17 day sailing adventure. We motored quite a bit on the second day and I noticed the the batteries were showing 12.4 volts several hours into the trip, I immediately powered the motor off and inspected the wiring suspecting a loose connection, turns out that everything was tight....or so it seemed.
At the end of the day I did a really deep dive and finally found that the positive post on the alternator itself was loose....inside the alternator. I could start the engine and when I reached in and pushed the post ever so slightly toward the side of the alternator it would move and the motor immediately loaded up, remove the finger and it would unload.
I removed and disassembled the alternator and found the two nuts that tighten the post to the rectifier had backed off causing a loose connection. There had been a good bit of arcing going on in there and the back of the bottom nut was pretty much gone, the rectifier itself also had a bit of damage to it as does the positive post itself.
I was able to clean things up and tighten the post down to the rectifier and got everything working again but I'll definitely need to go thru the entire alternator and replace a few parts.
The moral of this story is....don't just check the connections, check every component you can and suspect everything. The alternator was brand new just two years ago so it never rose to the surface on my suspect list....although it was in fact the problem to begin with.

[KWKloeber]

Check all connections and determine whether the field excite circuit has constant V from the panel and that the connection st the alt is good. Which model no. alt do you have?

Pull it if you find all else is apparently ok and have a trusted auto elec shop bench test it.

[waughoo]

Okay gang... here is what I have: ALT-1010AS 65amp self exciting alternator.  I had ONE remaining gummy bear plug at the engine pannel so I replaced that with the same deutsch connectors I used down at the engine bay.  I also have a REALLY old remote regulator (Ample Power Automatic 3-Step deep cycle regulator) and the connections there were pretty sour looking so I replaced those.  I tested the system after all that and it worked after a bit, then stopped again.

I am beginning to suspect the self exciting part of my alternator.  Does the next logical step here point towards removing the alternator for testing?  I would also like to hear if anyone has suggestions on a replacement as that might be in my very near future.

https://www.unipoint.com.tw/product_info_page.php?p_id=71

[LogoFreak]

Upgrade opportunity? High output alternator and a wakespeed ws500 external regulator? 

[waughoo]

Yes... that is exactly what I want to install, just not in the summer when I had JUST got done spending BIG dollars on the furnace install amongst a pile of other little things.  I might have to go exonomy right now to get by.

[KWKloeber]

(BIG) if that’s the cause…

My understanding is that SEs are not so good on diesels - RPM is too low.  Try reving it up high to see if she excites - it may have lost the residual magnetism. If you search for SE alt info you may find tips on getting her remagnitized so that she excites.

[waughoo]

Reving does not seem to do the trick.  I am likely going for replacement, but need to keep it simple and keep the costs down.  Suggestions?

[KWKloeber]

Reving does not seem to do the trick.  I am likely going for replacement, but need to keep it simple and keep the costs down.  Suggestions?

IIWMAlt it would depend if I’m going to upgrade next season and can get away w/ just a throwaway, offshore motorola knock off of what came OEM, or one that’s going to meet future needs, weighed against the cost of rebuilding it (which, uhhh, is how much…???)

[Patches]

Alex:

I've got some spare Leece Neville OEM alternators, including--I think--a 70 amp version which is NOS.  PM me if that would help you.  I'm on Bainbridge Island, and I'll let you have it for my cost.  We can do a handoff at the Bainbridge ferry terminal.

Patches