So I have a 99 Nissan Maxima GLE bought it in late may, within the first month the Alternator went out, So I replaced it with a New aftermarket one, It ran fine for another month and then it to has gone out, Well the big kicker is after about a week of sitting and not turning it on (due to alternator not charging battery) I walk outside and low and behold their is smoke coming from under my hood, So I pop the hood and instantly notice the alternator is on fire! So I disconnected the battery and was able to put out the fire with some water, My question is what in the hell would cause 2 alternators to burn out and then my alternator to catch on fire when the car had not even been touched. thanks a bunch!

Drew.

 

your alternator cought on fire when you hadnt touched the car in how long?

 

Umm arson? I don't see how else this could happen.

 

It sat in the driveway for a little over a week, Then I just happened to stumble outside and luckily catch it just starting to burn, The damage from the fire was restricted to the alternator and a small area around it, Will have to replace the wires that plug into the alternator when I replace the alternator, But dont want to do that until I find out what the hell is causing it to eat alternators every month and then cause random fires.

 

Your guess is as good as mine, Wasnt arson or im sure it would be more then the alternator that was on fire!

 

make sure coolant is not leaking into it, i had this happen to me, a small leak dripping from the water outlet, causing it to arc when running.

 

Also make sure that there isn't any engine oil leaking onto your alternator. I had oil leaking from my valve cover gasket when I bought my car, and after a month I noticed light smoke coming from my under my hood while driving and not too long after my alternator died.

Weird that your alternator caught on fire with your car just sitting there tho

 

A bad diode can cause a direct short in the alternator.

 

All these answers make sense. But only if the car was on..

 

spontaneous combustion?

 

There was an Alternator recall, but I think that only pertains to the 97 and possibly 98? but the non running thing makes no sense to me, on that note, what and when does the ALT fuse actually protect? mine did not go bad (fuse)when the Alternator took a dump.

 

and i thought my boys center console was a nightmare.

 

You sure your plug is in good condition? Maybe there something connected wrong or there's a short in the alternator plug or somewhere else.....

 

I can only imagine some sort of electrical connection (duh).

Let us start with a recap:

• Your car was simply sitting, nothing in, nothing out.
• A week later, your car, again untouched, is on fire near/at/in the alternator.

Now for my random stabbing in the dark:

• Arson, as some of us have guessed.
  • Someone hates you.
• An electrical issue.
  The only things that can cause heat in a otherwise cold engine other than another person, is the sun, electricity, and G*d.
  • Assuming that G*d doesn't hate you, we are left with the sun, and electricity:
    • Sun
      Was it possible that somehow, it was hot enough for something to have caught fire, and very VERY coincidentally, your alternator that you replaced was the only thing that caught fire?
    • Electricity:
      I have no knowledge of how the charging system works, but again, stabbing in the dark, perhaps a relay that is supposed to be "turned off" be going bad causing a direct connection between your alternator and the battery?
      Since this connection is somehow stuck on, and your car is not getting any sort of cooling, or is simply doing a short circuit, between the battery and the alternator, could this be the cause of the fire?
      I can only assume that it took a while for the weak point to fail and allow more current to pass, causing enough heat to be produced and start a fire.
      • I assume that the alternator is connected directly to the battery, and back, through a common ground. Again, I have no idea how the charging system works.

Good Luck.

EDIT:
Oh, as for where to start, I say start with continuity testing between the battery posts and the wire going to the alternator. If you can, try with the car off, then somehow on, but not engine running (for safety).
If I think of any other ideas, I will post here again.

Oh, and I just do not like typing out the word "G*d". Not that I have any issues, just weird OCD.

 

Thick charging wire going from alternator to the battery is always connected, even without the key. There's only one big fuse between them. The most probable reason: the diodes inside the alternator went bad and let battery discharge through the alternator. This could create that smoke.