Rebuilding an alternator

[callistov42]

My 100 amp Balmar alternator has been intermittent for a while and yesterday it just quit charging. I put the spare on and all is good. Question... boat (and alternator and captain) are in St Martin. They won't let me fly with the old alternator (I tried with a starter and had to throw it away) so I would have to ship it to get it back to Texas. Is it worth it to have it rebuilt at a local alternator shop? Is it as good an alternator if it is rebuilt?

[Jammer]

When they fail electrically, usually it's the diodes that go. Any shop can replace them. You would want to be sure they use the same ones Balmar did if you want the same performance. A complete overhaul would include bearings and (if the alternator has them) slip rings or brushes.


Properly repaired you'll get long life, similar to new.


Diodes fail due to heat. If it failed early, might want to consider better ventilation, or one of the regulators that has a temperature sensor and that reduces output if the alternators is hot.

[callistov42]

Thanks!
I got 10 years out of it so no complaints at all! I'll ship it back to Texas and have it rebuilt. New replacement is north of $600!

[donradcliffe]

Could be a $15 set of brushes. Put an ohmmeter across the field and turn the rotor.

[mrmarcocecchi74]

Why don't you try to fix it by yourself!?
In the end is "just a car alternator", fancy or not....
something like this

https://www.youtube.com/watch?v=hmx2...rr-RandomChris

[witzgall]

Chris from Balmar here. If the failure happened as you describe, and nothing was loose, then the brushes are the prime suspect. They are a wear item with a long but not infinite life. A good rebuilding shop should get it back into service for you.

Chris

[rwidman]

A good alternator shop should be able to rebuild that to as good as new.

[Lake-Effect]

A good alternator shop should be able to... oh wait that's been said already.


(I briefly worked for a marine diesel repair place, and we regularly got Balmars and other alternators repaired or rebuilt at one of the city's best automotive alternator rebuilders.)

[Dsanduril]

Originally Posted by callistov42

Thanks!
I got 10 years out of it so no complaints at all! I'll ship it back to Texas and have it rebuilt. New replacement is north of $600!

If Chris is right, or even if it's the diodes you should be able to find a shop in St. Martin that can do the work. Save you the shipping back and forth. Heck, there's a NAPA auto parts there that should be able to point you in the right direction.

Auto electrics is one of the most ubiquitous professions around, and smaller places actually have people that know how to rebuild rather than replace.