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Failing alternator

1995 F150 5.8 258k

Hey guys! After 25 years, my alternator has had enough! Battery is sitting at 12.8V but drops to 11.8V with engine on and even further to 11.3V under load, so I’m thinking bad diode?

Wondering where is the best place to get reliable alternators? I’ve heard autozone’s warranty is nice...but that you could be having to use said warranty every 12 months. Is mine worth rebuilding? I’m not savvy with electrical, but would be willing to ship it out for repair if you guys think it would hold up better than these reman ones? Any good ones out of rock auto?



Charter Member
IMO, the real question when evaluating rebuilt parts, like alternators, is one of what exactly is the meaning of rebuilt. Did they only fix the problem itself, clean it, and put it up for sale (usually for cheap)? Or did they do a "real" rebuild, did they replace all significant wear items (bearings, brushes, etc), important electrical items (ex, diode pack), and in the case of an alternator, polish the commutator, and in the end, price this accordingly given the higher level of quality and reliability (and charge even more $ for better parts as opposed to cheap ones made in Ding Wong). With this understood, now you get to decide what you want under your hood on a night where there's a foot of snow on the ground, it's snowing hard, and you've got 150 miles to burn before you're home. FWIW, me bought a NAPA rebuild with a lifetime warranty, it wasn't cheap, it's the same one that was put in by me over 10 years ago, and in the name of reliability, it was worth every nickle spent.
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Tonto Papadapolous
There are also local shops that rebuild alternators. Look for a reliable one that has been in business for awhile. I also had the guts of my last one upgraded from 60 amps to 100 amps. I have also had NAPA and had good luck with those.