Renewed alternator issues

[ewengstrom]

Apologies for the long post...I type very fast.....
Last year I'd posted on a thread that Alex started about his alternator puking and reported that my practically new alternator had also puked, the cause was that the nuts securing the positive post to the rectifier had loosened up inside the alternator (it's an AMPIT-100-ER from Compass Marine) and it started arcing. Since I was away from home on day 2 of a 17 day trip, I was able to clean it up and tighten the nuts down again and continued on my merry way. When I got home I removed the alternator and replaced the partially melted rectifier and nuts and it's been fine....for exactly one year.
This past weekend the exact same thing happened....the tach started dropping to zero.....then it would pop back up....over and over. I shut the engine down and started poking around and once again I found the positive post had loosened up inside the alternator and the arcing has fried the new rectifier.
I'm at a bit of a loss, the system is practically new, I'm using a Balmar 614 regulator with alternator temp sensor and all the wiring in the charging circuit is new and appropriately sized. I can't help but to wonder if there is some sort of heat issue going on with the alternator that is causing these nuts to back off and hence causing the arcing.
I don't want to give up on this alternator, Rod built it and I'm confident it is still good...once I put a new rectifier in it that is.....but I also don't want to replace rectifiers every year either.
Anyone come upon this type if issue before and if so, what was your cure????

[Ron Hill]

Eric : When I had problems with my duel output alternator (years ago) I took it to a alternator repair shop in Colonial Beach!!  Forgot the name of the shop. You might see if they are still in business?

A thought

[KWKloeber]

Did you Loctite it?

[ewengstrom]

Ron, I believe I do know where that business is!!! Perhaps I'll give them a shot.

KW, I did not find any evidence of Loctite on it the first time this happened, but when I reassembled it I did put a second nut on it this last time and tensioned it against the first to "lock" it in place.

[mainesail]

Apologies for the long post...I type very fast.....
Last year I'd posted on a thread that Alex started about his alternator puking and reported that my practically new alternator had also puked, the cause was that the nuts securing the positive post to the rectifier had loosened up inside the alternator (it's an AMPIT-100-ER from Compass Marine) and it started arcing. Since I was away from home on day 2 of a 17 day trip, I was able to clean it up and tighten the nuts down again and continued on my merry way. When I got home I removed the alternator and replaced the partially melted rectifier and nuts and it's been fine....for exactly one year.
This past weekend the exact same thing happened....the tach started dropping to zero.....then it would pop back up....over and over. I shut the engine down and started poking around and once again I found the positive post had loosened up inside the alternator and the arcing has fried the new rectifier.
I'm at a bit of a loss, the system is practically new, I'm using a Balmar 614 regulator with alternator temp sensor and all the wiring in the charging circuit is new and appropriately sized. I can't help but to wonder if there is some sort of heat issue going on with the alternator that is causing these nuts to back off and hence causing the arcing.
I don't want to give up on this alternator, Rod built it and I'm confident it is still good...once I put a new rectifier in it that is.....but I also don't want to replace rectifiers every year either.
Anyone come upon this type if issue before and if so, what was your cure????

What model # rectifier did you replace it with? When tightening B+ a thin spanner wrench should be used to prevent the B+  stud from spinning. If you twist it when tightening B+ it can come loose at the rectifier end. What batteries are you charging?

[ewengstrom]

Hey Rod, there was no model number on the old one, I ended up using a DR5042 as a replacement.
I've been quite careful when tightening anything on the alternator, I didn't want a repeat....I didn't see any evidence of loctite on the nut for the rectifier but I'm curious if that would be something to avoid...or is it a good idea?
My battery bank is four Trojan 6V batteries.

[mainesail]

Hey Rod, there was no model number on the old one, I ended up using a DR5042 as a replacement.
I've been quite careful when tightening anything on the alternator, I didn't want a repeat....I didn't see any evidence of loctite on the nut for the rectifier but I'm curious if that would be something to avoid...or is it a good idea?
My battery bank is four Trojan 6V batteries.

We used 70A diode rectifiers and we had them made by Regitar. You won't find a drop in replacement in the same form factor. For your bank the 50A diode rectifier will work but it gets hotter than the 70A. This expansion contraction can loosen  the nut. Two nuts, what you've done, also works. You can try red loc-tite but it softens when hot..

The most critical part is getting a very thin spanner wrench on thr square part of the stud..

[ewengstrom]

Rod,
Giving your replies a good bit of thought I'm inclined to agree that this problem may have been of my own making. I've never had to worry about using a spanner wrench when tightening the nut on the B+ post anytime in the past....but honestly, this explanation makes sense. I also hope this thread helps folks figure out something like this in the future.....it really is quite frustrating.

I'm also going to take a hard look at the cable itself as it is not attached to the engine anywhere other than the B+ post and I'm wondering if when the motor vibrates at lower RPM's it is actually working the post around inside the alternator. Once I get back to reinstalling the alternator I'll address this possibility and report back on the findings.

By some chance might you have one of the original 70A rectifiers and a B+ post assembly for the AMPIT-100-ER available? I'd very happily purchase it from you rather than attempt to source it elsewhere.

[Ron Hill]

Eric : You've got the alternator repair shop right there in town (Colonial Beech Va)  I'd surely let them take a look at it!!!  That's their business'!!

Because Colonial Beach is a small village, I'll bet that alternator shop is no more that a couple of hundred yards away form your boat!!!

A thought

[mainesail]

Rod,
Giving your replies a good bit of thought I'm inclined to agree that this problem may have been of my own making. I've never had to worry about using a spanner wrench when tightening the nut on the B+ post anytime in the past....but honestly, this explanation makes sense. I also hope this thread helps folks figure out something like this in the future.....it really is quite frustrating.

I'm also going to take a hard look at the cable itself as it is not attached to the engine anywhere other than the B+ post and I'm wondering if when the motor vibrates at lower RPM's it is actually working the post around inside the alternator. Once I get back to reinstalling the alternator I'll address this possibility and report back on the findings.

By some chance might you have one of the original 70A rectifiers and a B+ post assembly for the AMPIT-100-ER available? I'd very happily purchase it from you rather than attempt to source it elsewhere.

I don't have any rectifiers left we had to order them 300 at a time and we were about to place an order when I had to close my business. My buddy Gene who used to be at Regitar left and  joined another company..

I have plenty of B+ stud kits. compassmarineservices@gmail.com