Quote:
Originally Posted by apex996
I have recently discovered that some cars have an alternator "clutching pulley" that freewheels during specific usage.
Q: Does anyone have an informed mind on exactly how and when the special pulley does its thing?...
1. Disengages/unlocks only at high rpm?
2. Any known alt failures.... IF a standard pulley is used instead?
I need your input asap as I need to resolve my Carrera's issue right away. Im about to swap it out with another but need to it figure out
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I personally replaced my 996 alternator two weeks ago with a reman. My 911 ran sweet! (+ a new Optima red top batt.) Saw about 14v at all times. I think it started failing yesterday. 
Im hearing a low tone whine, smelling a burnt odor and the voltage had dropped to a varying 12-12.7 v.
After some digging on the web I now see that there are TWO variants. Some vendors list one or the other for the same model /yr.. with no details on it.
I now believe I originally had the the clutching/freewheeling pulley and my reman may of died because of some kind of non -compatibility . 
Any thoughts? I would appreciate any web-links to a source of info as well.
Matt |
A couple of questions: Is your car a Tiptronic? If it is, it has a higher amperage alternator (and battery) than the manual trans cars. Do you know what the output rating of the replacement unit is? If yours is a Tip, and you put a manual trans alternator in it, that can be a problem under high electrical load conditions because it simply cannot keep up.
The declutching alternator pulley is a Bosch item that is use on a bunch of different cars, even including some Fords. It is designed to free wheel at higher RPM’s, much like the old declutching fans did. We have had cars with the declutch unit start making noise when the declutching unit started to die, which is an easy fix, provided you have the correct tool to get the declutching unit off. I am not aware of anyone having a unit fail because they went from a declutching style to a fixed pulley style unit, provided the unit was the correct output.
I’d pull out the replacement unit and have it checked; if it is the problem, make sure you get the correct output unit to match your car, and reinstall it with the declutching pulley. Both your fuel economy and HP output will benefit (albeit slightly) from it….