Are re-built alternators as good as new?

Why or why not? What constitutes “re-built”? What are the common practices in the industry to rebuild one that has gone bad? I have heard from a buddy mechanic that they have 40% failing rate compared to new ones…


I tend to keep vehicles for a long time, and as a result, I’ve had starters and alternators replaced many times.

In my experience, there’s no noticeable difference in the life-span of those particular replacement parts–but that’s just my experience.

OTOH, I did have one replaced alternator that went bad after only a year. So. . . it depends.

A well-rebuilt alternator can be essentially as good as a new one. Some components of alternators suffer no significant stress even with years of use.

A cheaply rebuilt alternator won’t be so good. Different brands have different reliability rates. If you shop for the lowest price, you increase the likelihood of getting lower quality.

Brand new alternators are often tough to find, and when available tend to be godawful expensive. If you really want a new one, make sure it’s crystal clear what you mean by “new.” To some folks, that means still clean in the box from the rebuild supplier, “new” (to them) as opposed to “used.”

I had a rebuilt one that failed because the cheap bolts holding it together failed, but I replaced it with another rebuilt one.

Apparently only the windings on the rotor get re-done; the stator coils are difficult or impossible to re-wind, so I suppose it is more likely that these would fail from old age/wear than it is on a brand new unit.

The original (OEM) alternator on our Safari van bit the dust last year. I removed it, but then was left with a decision. Should I…

a) Purchase a new alternator?
b) Purchase a re-built alternator?
c) Have it repaired?

I chose c) for the following reasons:

  1. By having it repaired, I am guaranteed it will fit, have the correct pulley size, etc.

  2. By having it repaired, I know what went wrong (Windings? Diodes? Brushes?) This might give me a clue as to what caused the problem.

  3. With a re-built alternator, I have no idea what was replaced and the quality of the components used.

  4. With a new alternator, unless it is truly OEM I do not know if it meets stringent GM specs. (It has been my experience that no after-market product lasts as long as the original.)

  5. Throwing my alternator away is wasteful. (I hate the “throwaway” mentality. If it can be repaired at a reasonable cost, then it should be repaired, IMO.)

So I found a guy with a shop called “The Electric Garage.” After talking with him a while I gained quite a bit of confidence in him. He ended up doing excellent work.

You have four options when your alternator goes bad:[ul][li]Buy a new one[/li][li]Buy a rebuilt one[/li][li]Have yours rebuilt[/li][li]Buy a used one[/ul]Of these I would always choose buying a rebuilt one.[/li]
I don’t recommend buying a new one simply because it will be too expensive, several hundred dollars. And its a waste, you don’t need to replace the old one with a whole, brand new one.

I don’t recommend having your old one rebuilt simply because buying a rebuilt one is faster, no more expensive, and basically the exact same thing as having your old one rebuilt (they take your old one as a ‘core’, rebuild it, and sell it to someone else later). You can argue that the rebuilt one you get might not be as good as your old one, but the reverse could just as easily be true too. Besides, parts stores always guarantee them anyway.

And I only recommend getting a used one from a junkyard as a last resort (if you’re strapped for cash or can’t find one anyplace else). Used electrical parts are a total crapshoot. It might last 10 years or 10 minutes, there’s no way to tell.

I hate to break it to you, but b) and c) are basically the same choice

Usually the rebuilt comes sans pulley and you transfer your old. Admittly there is a chance that the wrong unit got put into the box, but with a quality rebuild you have about a 99.9% chance of getting the right unit the first time. In 35+ years of working on cars, I don’t think I have pulled a wrong alternator from the box more than once or twice.

I will give that one to you. Advantage having your unit rebuilt

Unless you are sourcing the parts, you are going off the word and reputation of the guy doing the work, same as buying a rebuilt.

First off I seriously doubt that you could find a truly new alternator for your car, from any source, much less an aftermarket source. I will agree with you about the quality of many aftermarket parts. Not all, but many. Also your comment about stringent GM spec is the funniest line I have read all day. Thanks for the laugh.

No one throws away alternators. Your old alternator goes back to the rebuilder to be rebuilt for the next customer. This is why when you buy a rebuilt part you are charged a core charge. The core is your old part. When you return it, the core charge is refunded to you. This is how the rebuilder gets alternators to rebuild in the first place.

No arguement there, you should always find someone who does good work, and not shop just for price.

Here is the deal, there are several part of a car, that while some of the insides may wear out, the outer case and other interior parts are fairly bullet proof. These parts are usually rebuilt. A list of these part would include, Engines, Transmissions, alternators, starters, brake calipers, and sometimes master cylinders, and radios.
A quality rebuild would entail the following steps.
[li]clean old unit[/li][li]inspect for worn/damaged parts to be replaced[/li][li]replacement of bad parts along with other parts identified as wear items*[/li][li]reassembly[/li][li]test of unit on bench[/li][li]package and ship[/li][/ul]

  • in the case of an alternator, this might be the unit has a bad fron bearing, and the brushes are replaced as a matter of course.

I work for a car company now. For the items listed above, the only time a new unit is supplied is when we have a car that is not yet sold. Then by law, we have to supply a new unit and cannot install a rebuilt. These have to special ordered and boy are they pricy.

Rick –I found someone whom I thought would do excellent work on the alternator. As it turns out he did do excellent work; he also explained what he did and gave me the defective parts. (I’m an engineer, so from my perspective I appreciated this interaction.) And I would much rather pay him $100 to repair my alternator than pay Pep Boys $100 for a so-called “re-built” unit that was assembled in Mexico using parts of unknown quality by people of unknown skill levels.