91 3.1 alternator problems

I have had to put 4 alternator's in, within the last 5 months. Two of them, the rear bearings went out on. Changed one out because it just stopped charging, now the last one. My volt meter is showing around 15 volts, not noticing the light during the day, The Bat light will flicker a bit, stay on for a few seconds go out for a while, and then do it all over again. My gauge doest show any fluctuation.
have 100 amp Alt. new battery, I can't believe this many alternators in a row would be bad, is there maybe somewhere else I should be looking for a problem.

I'd get my money back and go buy a different brand from another parts store.

What brand/parts store? Apparently chains like pep boys have their parts such as alternators actually made to fail quickly. Why would they do this? Each trip to their store to exchange for another means you may pick up some extra goodies such as oil, filters, etc. Unfortunately I just went through this and next time will spend the extra cash to get a quality unit from a real parts store.

these were oem reman delco alternators from Napa, never heard of pep boys. That is why I maybe figured there was a problem with the truck somewhere causing early failure. Here is the order in which I went through them the first was the one on the truck when I got it... rear bearing failure. replaced that one, and had a bearing failure on the next one. changed that one out, the next one just up and died, didn't have any bearing noise when replaced. now the one now is the one that is just getting the Batt. light flicker only at night. I am not noticeing it during the day at all. Like I said, voltmeter continues to show 15 volt or so. Might just have to bring it in and have a complete charging system checked. Was just hoping that there could be something I could check without having to spend any money. Already spend enough just keeping fuel in it.

Thanks

I got an Autolite Platnium All-New alternator from Kragen Auto Parts (www.partsamerica.com) and works perfect. first time replacing the alernator on the rodeo. i can run at an idle with my 1,000 watt amp "pushin" my 2-10" subs and the headlights bearly flicker.