How long should an alternator last?

I had the alternator replaced in my 2006 Mercury Grand Marquis not even 2 yrs ago. Well d@$m it went out again today. I thought maybe they are rebuilt and the mechanic got one that was not built with good parts. I don't know a lot about this.

But I looked on Auto Zone website and they are listing them as New. I don't know where he is buying his from.

Shouldn't it have lasted longer than under 2 years. I put less than 20,000 miles on my car during that time.

Yes, I agree with you. They generally last at least 6 yrs & can last up to 10 or more.
What went bad on it? Not charging anymore? Then a contributing factor here would be a weak battery or main connections. Bad batteries will kill Alternators... Bad Alternators can kill batteries.

If it failed due to bearings and squeals or seized up, a contributing factor could be a failing belt tensioner or belt was put on too tight.

If you are able to take a photo of the part # area or label, I can usually tell where it may have been purchased, especially if it came from a chain store. BTW, most places will have the option of rebuilt or New.

[QUOTE=bellaCuba;7188450]Yes, I agree with you. They generally last at least 6 yrs & can last up to 10 or more.
What went bad on it? Not charging anymore? Then a contributing factor here would be a weak battery or main connections. Bad batteries will kill Alternators... Bad Alternators can kill batteries.

My knowledge of all of this is very little. They hooked it up to their 'whatever it's called' and he said it was the alternator and it drained my battery.

My car started doing just what it did last time turn signals were quitting, air conditioner, then the power steering started tightening so I was able to make it there before it quit.

My boyfriend has known this mechanic for years is the reason I go there so he trusts him. But this doesn't make sense to him or me. They had already closed for him to call and ask any more questions. And I am broke so he paid for the last one and this one too. So I'm thankful he will but I don't like that he has too especially since it didn't last.

The durability of the alternator depends on many factors. you can find more details from here http://auto.howstuffworks.com/under-the-hood/car-part-longevity/how-long-alternators-last.htm
it's hard to say exactly how long an alternator can actually last. It depends on the car, the engine, the conditions in which it's used, how much electrical equipment it's regularly operating and so on. Some cars may lose an alternator at 40,000 miles.
The main factors affecting the durability is the electrical load climatical conditions.

Some times voltage regulator circuits( those semiconductor components) will face thermal runaway due to immense heat from IC engines, which can reduce the durability of alternator. Water logging to the internal rotary bushes and brushes will lead to immediate failure and short circuit.

Depends on so many factors... make/ model/ year.... condition of part All going well you could get 10 years out of it. But it's a bit like "how long is a piece of string"

Your voltage regulator should be changed whenever the alternator is changed. Was this done?

Your voltage regulator should be changed whenever the alternator is changed. Was this done?

Just a quick FYI: This is good advice for an older car, but... by the mid/late-1970s, most car companies had made the voltage regulator an internal part of the alternator. This practice continued through the 1990s. By the early 2000s, the function of voltage regulation had generally been incorporated into the car's ECU.

Although it would almost certainly carry a greater initial expense, I'd advise having the car tested by a Ford/Mercury dealer. If there has been a failure of one of the ECU circuits, their evaluation equipment would be more likely to find it.

It's also VERY possible that the problem that caused the two alternators to fail was poor electrical grounds. Rusty/corroded grounds can put extreme loads on the alternator because it has to work so much harder to charge the battery. Bad grounds (both at the two ends of the negative battery cable, as well as the other chassis grounds) can reduce the current flow in the charging system. Imagine the flow of electrons coming out of the alternator as water flowing from a garden hose. When ground terminals get rusty or corroded, it's like trying to force all that water through a soda straw! That will give you an idea of how hard the alternator has to work in those conditions. Many mechanics/techs overlook ground connections when servicing cars... it's just one more thing that car owners need to learn to watch for themselves.