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Original owner 02 Powerstroke F250. 170K miles. I just replaced my forth alternator due to bearing seizure. All pulleys look aligned, tensioner seems working fine. Count is: One OEM, one aftermarket local shop, one O'Reily, one NAPA (new not rebuilt). I could blame the auto parts houses but beginning to think it's another issue.
 

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I have replaced a lot of 95-2003 7.3 alternators but never for bearing failure. Something is definitely going on. You should have someone rev the engine up very slowly to 2200 RPM (that is the upper end of revs that any gearing makes that engine turn at 70-75 MPH) and see if there is any shaking of the alternator or any other weirdness with belt, etc.
From your post I think you are saying all the alternators failed from bearing issues. Did they all go about the same distance or did the OE one go a longer span and each replacement a lot less miles?
 

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Actually, OEM lasted less than 40K miles. Not sure about bearing failure in first two but think they are still in a barn. On the road but will check when back at the coup. Last two definitely bearing!
 

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One thing to check is to see if you have the right serpentine belt. There are two different belts that differ slightly in length depending upon whether or not you have the cold weather package. If you are supposed to have the longer belt, but instead you have the shorter belt, that could make it too tight and cause the bearings to fail. How tight is the belt?
 
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Well, that’s certainly a thought, think my original is behind the back seat as a spare. No tensioning issues installing new belt with any of the above alternators.
Thanks!
 

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Did you get the lifetime warranty alternator from O'Reilly's this time?
 

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Also look at the accessories you have installed if any. Even high power stereo systems. Normally a bearing failure on an alternator is not from tension, but instead from heat. Over loaded alternators get real hot. That's why the ambulance package was made with the extra alternator for all the gear. I had 2 alternators sieze, 8hrs after install on my backhoe. Because the mechanic didn't charge the batteries before re starting the hoe. Burned up both of them. Last one was glowing when it failed. I did the 3rd install, and the alternator came with a big cardboard card attached to it so you cant miss it, saying make sure to fully charge batteries before starting, or it may fail, and warranty is void if you don't. Wonder how the mechanic missed that , twice.
 

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Also, if yours came with no pulley, like mine did, on my truck I mean. THen that means you put the pulley on it. If you over tighten the nut, you ruin the bearings.
 
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Well, that’s certainly a thought, think my original is behind the back seat as a spare. No tensioning issues installing new belt with any of the above alternators.
Thanks!
Only if you are sure that it is the original, then is it possible to read a P/N?

What is the P/N of the belt currently installed?

My thought was the same as Don's, that you might have the wrong belt installed.
 
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