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Old 10-04-2004, 07:43 PM
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Question How many DIFFERENT 1989 300E alternators?

After swapping out the brush pack/ regulator on my elderly father's 1989 300e, I decided to replace the unit with a BOSCH FACTORY REBUILT UNIT.
The first one that I picked up locally was incorrect. Note, that I had not YET removed the troublemaker. Also note, this is a USA model, never been modified, with the original factory wiring harness. This harness on the original (faulty) alternator has the multiple push on connector (not the wires attatched to the alternator with bolts).
Evidently, for model year 1989, the spec calls for the "newer style connector" the bolts, NOT the multiple connector.
To make a long story shorter and more bearable, it appears that the car (1989) needs the alternator listed for a 1987 300e.
Even more frustrating, there seems to be a difference in the output shaft configuration.
The ORIGINAL unit had a longer output shaft, where as the (2nd) replacement has a SHORTER output shaft.........this REQUIRES a DIFFERENT 1/2 moon shaped KEYWAY which locks the fan and pully assy to the shaft.
When I first REPLACED the alternator a week ago, I installed what seemed to be CORRECT. I also replaced the serpentine belt for good measure.
500 miles later, the NEW serpentine belt was damaged and making a flapping sound.
Upon examination of the damaged belt, it appeared that the alternator PULLY was off the centerline of the rest of the pulleys by 1 groove.
Ok, I removed the offending alternator and went to the REPUTIBLE local parts place to see why. This was after I assumed perhaps the IDLER PULLY was was NOT, however, I am replacing it anyway. It has 160,000 miles on it and I had it apart anyway.
Today, I recently left the parts place with 2 alternators BOSCH AL65X, and BOSCH AL68X.
Some differences, One has the longer and slightly more NARROW SHAFT which fits all of the ORIGINAL spacers and pulley....HOWEVER, this unit MUST have another WASHER installed under the FACTORY ORIGINAL PULLEY to line up correctly.....This unit is the one that was on the vehicle functioning properly....EXCEPT FOR THE AFOREMENTIONED slight misalignment.
The OTHER unit is listed for a 1987 300E..........its housing is EXACTLY what I need...........HOWEVER, the factory ORIGINAL pulley and spacers will not ALL fit on the SHORTER OUTPUT SHAFT..........In ADDITION to requiring me to locate OR fabricate/modify a DIFFERENT keyway to fit correctly.
FIRST, my dilema. Do I go with the extra spacer under the pulley......OR do I use the unit with the shorter output shaft and REMOVE one spacer and get/fabricate/modify another key to fit the shaft?
Any thoughts out there from any of our esteemed and KNOWLEGABLE members?
Also, WHY would I be experiencing this type of QUIRKY parts matching?
Has ANYONE else been through something similar.
I WAS able to get an "AMERICAN" ie; non-metric key this evening. It would need to be filed down to fit.
Thank you all.
spo out

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Old 10-04-2004, 08:09 PM
Registered User
Join Date: Oct 2004
Location: England
Posts: 43

Go to main dealer and give our VIN number and you will be given (or it will be ordered for you) the same alternator that was on your car when it left the factory. That is all there is to it.

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Old 10-04-2004, 11:31 PM
Mike Murrell's Avatar
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Join Date: Feb 2000
Posts: 2,580
Looking at one web parts site I see one type for engine #'s up to 12-179741 and another for engine #'s from 12-179742. I suppose one uses the push-on connnector; the other fastened with the small nuts/washer(s).

Here's the details from one place. One of the photos shows the AL potion of the part number; the rest is indiscernable.

This might help you in dealing with the indy.

Did you take the orig. alt. to the indy to match it up the first time around? Doesn't sound like it.

Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
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