my alternator on my 1987 300e is shot. I want to buy my own alternator, and possibly replace it myself. I talked to a mechanic, and he said that bosch makes 2 lines of products, the kind they sell at pep boys/autozone (bad quality), and the kind they sell to mercedes. If i ordered from fastlane, or ******** az, would i be getting the higher quality alternator? Also, how much trouble is it to replace an alternator by yourself?

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87' 300E

I'd go with the people that offered a lifetime warranty.............

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Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

Auto Zone will do just that, but you'll spend every other weekend removing the thing and taking it back.

Find a legitimate provider.

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'91 300-SEL

sure you don't just need the screw in regulator for 20 bucks?

I got a rebuilt Bosch starter for my Diesel truck from Track auto....now Advance auto for $85 ....everyone else wanted $250 (rebuilt).....that was 7 years ago....never a problem yet.

Highest price place doesn't guarantee the highest quality...or the least problems.

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Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

My dads F150 is on it's 4th Napa/Autozone alt. They don't offer a lifetime warrenty on his anymore, 3 years I think.

I just went through this, I ordered a $200 alt from Autozone and it wasn't even a Bosch rebuild, some China crap. It didn't even have the right shaft in it, I returned it and bought a proper one from Fastlane. Fastlane sells very nice Bosch rebuilds and it cost me $200.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

I worked in an autoparts store for three years and saw lots and lots of perfectly good alternators getting returned as cores for rebuild. I really think there's little difference between the lifespan of rebuilt alternators. I think the biggest determinant of having a good experience from your alternator is by considering it as a "part" of your battery. A bad battery will kill a good alternator, and a bad alternator will kill a good battery. People get into vicious cycles and have no idea what is happening. Make sure your battery is holding a charge so the alternator doesn't get stressed, and make sure the alternator is putting out the correct voltage and current so battery doesn't get cooked. Unless the bearings or the windings are shot all you'll really need is the regulator. Two screws and you're done. It's not totally obvious how to diagnose a bad alternator. It's easier to diagnose a bad battery - charge it fully, let it sit overnight, and test it with a high-discharge tester (the kind that gets hot and has internal coils). An alternator needs a minimum voltage before it starts to work, so you can't charge a fully dead battery with an alternator...

Replacing an alternator is not all that difficult if you are comfortable with the operation of the serpentine belt. There's tensioner that is tucked away and has a 13mm hex fitting, near where the thermostat lives. Getting to a happy place with the serpentine belt is not effortless the first time you do it (or the second, third, or fourth times for people like me). Otherwise it's 3? bolts to remove the alternator from the housing, plus the wiring.

So to make a short story long, I'd go for the regulator and run a battery test before putting it in. (Also make sure your serpentine belt is tight enough. )That will confirm the diagnosis of a bad alternator and prevent you from killing a new alternator with a bad battery

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89 300te 222,222
92 300e 190,000

You might want to try to overhaul this yourself if you have time to keep the car down for a few days. You should be able to find the parts online doing a Google search for "alternator parts". You will most likely find that only one component is bad and in the worst case that would be a rotor. I got my Taurus rotor for under $30.00 the rebuilt price of an this alternator from Pep Boys was over $100. I will be willing to bet that you could get a Bosch rotor for under $75.00 and repalace everything else needed for a total of under $100,00. These are not difficult to rebuild but if you never did it before you may want to check out a book from the library to get familiar with checking diodes and other parts.

John Roncallo

when taking the alt to be bench tested - will the testing test the alt it self, or the voltage regulator, or the combo of the two together?

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1979 Thistle Green 300D 272,xxx miles
1984 Orient Red 300 D 4 spd Euro Import - 189,xxx miles
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Lofat Productions
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DR88:

I have used rebuilt alternators for over 30 years and the only stipulation I would make is buy from a good source and/or with a good warranty. As usual, this must be balanced by cost. Most online parts sources sell the Bosch premium rebuilt alternators which have always provided me good service. Europartsdirect, whslparts, exprsautoparts, etc have them for $142 up.

As far as difficulty to replace, it is quite easy basically, depending on one's experience. If you want to try it, get instructions (I can send you the info from the MB CD manual).

As far as rebuilding the alternator yourself, I would say that it would require more experience than just switching one out, and quite a bit more time (depending on the extent of the rebuild you would do).

Finally, I just replaced the alternator on my 300CE - took me 3 relaxed hours. The prior owner had done the brushes/regulator thing and it lasted 27,000 miles.

Cary

Lofat:

Bench testing an alternator should test everything.

Cary

Thank you for the reply

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1979 Thistle Green 300D 272,xxx miles
1984 Orient Red 300 D 4 spd Euro Import - 189,xxx miles
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Lofat Productions
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found an old guy, who runs a one man shop in homestead fl
$60 to rebuild my bosch 65amp from the 300sd
cash and drop off only sorry no CC no ship
and he did it in one hour!!!!!

Did he do anything besides replace the regulator/brush unit?

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2012 E350
2006 Callaway SC560