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Registered
1985 500 SEL
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175 Posts
Discussion Starter #1
I am in the process of upgrading my stock alternator to the 115 Amp model, but the 115 amp model has the pulley for a serpentine belt system.

For the time being, I want to keep the stock alternator intact just incase there is need to put it back onto the engine or possibly selling it at a later date.

Does anyone have a pulley that they want to sell? or
Do you know where I can find the Pulley?

Thanks.
 

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1985 300sd
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445 Posts
Uhh, exactly which 115 amp alternator did you get. Because the one that has been discussed in great detail here on the forum is the Bosch AL 129X, which definently uses a v-belt. There is even an individual on here who sells them for around $100, fully tested and ready to go. I have the AL 129X in my car, outside right now, and the mount was pretty straight forward, from what I have been told, only that it was a tight squeeze.
 

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1985 500 SEL
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175 Posts
Discussion Starter #3
That is exactly what I purchased. The Bosch AL129X. I purchased it from a member of this forum. Normally, I guess that you can just swap the pieces, but I want to keep the original together as a unit. That is why I am trying to find another pulley.

Is the installation as straight forward as it seems? Should there be anything that we should be aware of before beginning the installation?

Any extra info would be more than appreciated.

I know that this is a popular upgrade for the diesel engines, but has anyone ever done this on a gasoline engine?
 

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1985 300sd
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445 Posts
I still don't know what your are talking about. The AL129x uses a v-belt, and so does a 500sel, so what is your problem with the swap?
 

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Registered
1985 500 SEL
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175 Posts
Discussion Starter #5
Isn't it possible that the unit that you purchased already had the pulley changed for the v-groove belt? The AL129X that I purchased still has the pulley for the serpentine belt.
 

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87 420SEL, 89 560SL, 92 300TE
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62 Posts
I also have one of these alternators - I'm going to take it this weekend to a local alternator shop to have it thoroughly tested and "gone through" - replace anything needed. And yes, it has the serpentine belt pulley on it. As I understand it, many of these alternators floating around now came from Volvos with the serpentine setup.

BTW, Bosch alternators do not necessarily "come with" either the serpentine or V-groove pulleys - the manufacturers specify the pulleys they want when they place the order with Bosch. Since Bosch sells the same alternators to many manufacturers, you can see just about anything on a Bosch and it could be "stock".

Any local alternator shop should be able to mount the V-groove pulley onto the AL129X. Also, if you have a need for more low-RPM output from the alternator, a smaller-than-stock pulley can bump up the idle output somewhat at the cost of shortening the life of the alternator brushes. Most alternator shops will have a selection of sizes in these pulleys, since they interchange across a wide range of applications.

-Robert
 

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300 SEL (1989)
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369 Posts
I'd be interested in one of these alternators.
Read somewhere that they are fitted to SAAB or VOLVO's. Doesn't the pulley, whether ("V" or polyvee)
need to be adjusted to align it with the other driving components. Are all Bosh alternator shaft diameters the same?
 
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