Alternator Pulley ??

[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
**
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

[apex996]

I also see that Pelican offers the clutching pulley (aka freewheel lock)
No notes or specifics anywhere.

Pelican Parts - Product Information: 997-603-154-00-M14

[JFP in PA]

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
**
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….

[apex996]

Its a 6 spd and I did not install a Tiptronic unit.
The outputs are identical to the orig.

As I learn, I'm starting to think that the alt that I gave up as a core .. simply had a bad pulley that no longer stayed locked at the lower rpms. ( hence no output). It made no noises or other symptoms other than no output btw.
Wow, I'm freaking out. That core is long gone and I'm stuck with a dead unit with the crappy pulley. I bought mine from a nation wide parts store. I have a few costly days wait for another to arrive.



I see that the unit for sale here on Pelican has a pulley on it..
Basically no pulley notes or tech info ..whatsoever.

Pelican Parts - Product Information: 996-603-012-2X-M14

[apex996]

Regarding the old unit:
I remember that the pulley free-wheeled ( independently from the internals) in my hand prior to giving it up as a core. . I assume it should be in the locked mode.. in the scenario.
At the time, I assumed that the something snapped inside and had no clue that the pulley was a clutching type. Serves me right, being a rookie 996 owner.

matt

[apex996]

its a 6 spd, not Tip.
The amps... identical to the orig unit too.

Thanks for replying

matt

[apex996]

I do see Pelican offers the clutching pulley.
.
I also see that they offer a re-man, the unit is pictured with a pulley.
No notes or tech info on swapping pullies there.

matt

[JFP in PA]

First, to either remove or install the clutch style pulley, you are going to need one of these special tools (about $35):



This hold the alternator shaft while tightening the pulley. The rest is just torque specs.....

[apex996]

ah, a VERY special tool. This is getting more unpleasant.
Lovely.

K, I see them on Ebay.
I really appreciate the info.

matt

[JFP in PA]

The reason you need the tool is that the shaft and the nut are both internally splined, hence the weird look...........

[FPB111]

The 6 speed has the freewheeling pulley, with a SPRAG clutch, to allow the alternator to freewheel and bleed off some inertia between 'abrupt' higher RPM engine speed changes. This helps to prevent belt shredding and or jumping ship. Tips are not as likely to have the more abrupt RPM changes between shifts so Porsche did not put the freewheeling pulleys on those alternators.

Some info here.
http://www.ntn.co.jp/english/products/review/pdf/NTN_TR75_en_P124.pdf

[apex996]

Originally Posted by FPB111

The 6 speed has the freewheeling pulley, with a SPRAG clutch, to allow the alternator to freewheel and bleed off some inertia between 'abrupt' higher RPM engine speed changes. This helps to prevent belt shredding and or jumping ship. Tips are not as likely to have the more abrupt RPM changes between shifts so Porsche did not put the freewheeling pulleys on those alternators.

Some info here.
http://www.ntn.co.jp/english/products/review/pdf/NTN_TR75_en_P124.pdf

Thank you very much for the info ! It gives me much of what I was needing/ looking for. I really eat this stuff up !!

*** As it turns out, the reman alt I rcv'd was for a Tiptronic... even thogh I clearly asked for a 6spd unit. After I *****ed a while, they ended up comp'ing me a reman Bosch unit for no extra charge. ( a net loss of +$220 for them)


The runs great. Lets see if she holds...

MATT

[benhchang]

Apex 996, Did your reman bosch alternator have the clutch style pulley?

Ben