Disconnect the battery and pull the regulator. Check for any corrosion on the grounded face that contacts the alternator housing. Also, check the alternator housing itself. (No, tight screws are not a good enough test.)

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Sam

84 300SD 350K+ miles ( Blue Belle )

4 alternators went bad? Can't believe it's bad luck!

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Yeah, they're all AZ remans. They're warranty replacements so no cash just time. And given my apparent lack of troubleshooting skills, my time is pretty worthless. Ha! Anyway, I'm going to replace every major cable I can in this damn thing I guess. No clue what to do other than throw parts at it. I've got an alt here sitting on the bench I can reman myself. Any opinion on manufacturers for the guts of it?

Bring the alternator into Autozone to have it tested to verify that it is bad. Have you done that with the first 3 alts?

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Yeah, they test em to verify before accepting them back.

What brand of reman alternator is autozone providing? My experience has been the "OEM" brand remans are absolute crap. One lasted a year, another barely 2k miles.

You've checked and checked and checked the cars system, the one constant remains the autozone source. The charging system is very simple on these cars. 4 alternators in a row seems crazy, but then again its 4 alternators in a row all from the same source.

Id consider changing it up. Id buy either a genuine bosch reman from PP or similar (in boh cases the solution to my bad alternators), or id pull a original alternator from a junk car and see what either do

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This post brought to you by Carl's Jr.

Every thread I read, says that a bad ground or connection will cause the alternators to keep frying......says the connector on the back of the alternator could cause the problem or a bad ground connection.....something causing the voltage to not move along....

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