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Thread: How long to alternators last?

  1. #1

    Default How long to alternators last?

    How long to alternators last on a 4.7? Maybe I'm a bit paranoid because I've had three alternators go out on vehicles I've owned, but my WJ has 130K miles on it and I was wondering if I should replace it soon for peace of mind.

  2. #2
    Registered DaveG55's Avatar
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    May as well ask how long a power steering pump lasts, or the compressor, or the water pump...
    Just like any part on a car, it fails when it fails.
    My alternator on my ZJ lasted 249,000 miles, my water pump, 120k and power steering pump, 215k.
    You can spend $100 on a new one if you want but the fact is even the new one could go out in a month, 6 months or 10 years. Personally, I don't see the piece of mind in that.
    And it's not like the evaperator that is worth replacing if your in the dash, the alternator is easy to get to and a fairly easy swap.
    Any sufficiently advanced technology is indistinguishable from magic.

  3. #3
    Registered No Limit's Avatar
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    Quote Originally Posted by DaveG55 View Post
    May as well ask how long a power steering pump lasts, or the compressor, or the water pump...
    Just like any part on a car, it fails when it fails.
    My alternator on my ZJ lasted 249,000 miles, my water pump, 120k and power steering pump, 215k.
    You can spend $100 on a new one if you want but the fact is even the new one could go out in a month, 6 months or 10 years. Personally, I don't see the piece of mind in that.
    And it's not like the evaperator that is worth replacing if your in the dash, the alternator is easy to get to and a fairly easy swap.
    TRUE. Since I owned a 1987 corvette that just "ate" alternators it TOO just sat up top like the alternator does in my '02 and can very easily be swapped out. The vette took (no kidding) about 10 minutes but it sure "ate" alternators. I have about 160K on my Jeep and I won't throw good money at that part until it fails. If it fails on a trip I have AAA. Everybody is different but MY RULE OF THUMB is to only spend money on a part that "MIGHT" be questionable if it takes mroe labor vs. part expense to get to it (for instance, DAVE G55 suggestion about the evaporator). You should do it and the heater core together regardless if they failed becauz of the labor involved. But just let the alternator fail......What if the vehicle was totaled the next week?....You lose out on the $$$$ for just a Gamble.

    Having said that ...let me say this....I'm the worst when it comes to throwing money at parts to give me a peace of mind but certain parts are "unpredictable" and even when new can fail imminently.
    '02 JGC Laredo - Black 4.7L/V8, Leather heated seats, Sunroof, Tow package, 10-disc CD, EVIC w/homelink, 2WD with rear D44 Vari-Lok, White gauges from Limited, ....as parts fail mods will prevail.

  4. #4

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    A bad alt will not strand you provded you notice the low volts and aren't too far from home. Mine failed 50 mi from home once and I made it back before the batt was dead. Most people don't bother to look at gauges or know what they are looking at and don't know anythings wrong until the car stalls or doesn't start.

  5. #5
    Registered VicPick58's Avatar
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    The alternator on my 2000 Laredo 4.7 lasted 240k miles, and of course it was real early in the morning (dark) and 50 miles from home. But even with the headlights on I was able to drive to the nearest dealer and wait in the service drive until they opened.

    Turned out my battery had a short and was drawing too much power from the alternator, so it would probably have lasted longer if the battery had not gone bad.

    Now I replace the battery at least every three years. You are more likely to get stranded by a bad battery than the alternator.
    2004 Overland Traded in at 218k miles on a new 2012 4Runner Trail Edition. 4-21-12

    2000 Laredo 4.7 Q-Drive, was still running good when SOLD at 281,340 miles.

  6. #6

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    I do have AAA, but the thought occured to me it would still suck to break down 500 miles from home on the Sunday before the 4th of July. Maybe I need some Xanax instead of a new alternator. Anyway I was also in the position of having the heater core replaced, so there was the balance between replacing stuff just because there was access versus keeping the already high cost under control. In the end I left the evaporator because there was nothing visably wrong with it and the mechanic pointed out a new one could go bad too, had the evaporator door replaced since it was already starting to wear. Left the actuators because I heard they tend not to fail, Blend doors were previously done with Blendoor, I wanted to get the dash removal kit with the metal spindles to replace the no-dash removal kit but I coudln't get it in time so the plastic spindles went back in.

  7. #7

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    Well since the part that mainly fails at lower mileage #'s is located in your PCM(voltage regulator) and not in the alternator they tend to last a long time in newer Jeeps since the voltage regulator is not subjected to the stress and heat from being bolted on the alternator.But like all parts they do wearout after time but 150k+ is not hard to do with a newer Jeep alternator,200k+ is average from what I've run into at work.
    I drive a Liberty,laugh now.

    Sitting on 35's,HP44,RockJock60,and 4:3 AtlasII

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