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S4 Alternator bearing, slip ring, and voltage regulator check & questions

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S4 Alternator bearing, slip ring, and voltage regulator check & questions

 
Old 12-04-2011, 04:32 PM
  #16  
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Originally Posted by mark kibort View Post
really? why dont you tell me the difference then.
an alternator IS a motor that is being spun, not spinning something else.
An alternator has a fixed winding called a stator. The rotor is what what spins creating unrectified ac voltage. A starter and generator have fixed magnets in the case and the armature is what spins. A starter and generator will spin when voltage is applied. Remove the belt from an alternator and apply voltage. It will not spin because of the magnetic field it creates. An alternator and starter have totally different internal components.
Also stated in a previous reply, a diode trio and rectifier bridge are terms specific to GM alternators, mainly the SI series alternators.
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Old 12-04-2011, 05:20 PM
  #17  
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Originally Posted by ZEUS+ View Post
An alternator has a fixed winding called a stator. The rotor is what what spins creating unrectified ac voltage. A starter and generator have fixed magnets in the case and the armature is what spins. A starter and generator will spin when voltage is applied. Remove the belt from an alternator and apply voltage. It will not spin because of the magnetic field it creates. An alternator and starter have totally different internal components.
Also stated in a previous reply, a diode trio and rectifier bridge are terms specific to GM alternators, mainly the SI series alternators.
Woops, you are right. kind of. what is the rotor, as it has windings too,right? actually, even if there is a stator, it technically can be an armature too, even if it is fixed.
Its not a PM rotor, because it has wires, and the commutator is connected to it, via those wires. so, its an armature, no? if it didn have a commutator, it woud be a rotor of an induction motor. but, the wires and communtator technically make it an armature. Im sure it wouldnt run like a motor with power applied to the commutator brushes, but i bet you could modify it to run.


armature definition:

2.Any moving part of an electrical machine in which a voltage is induced by a magnetic field.

so, in an alternator, since the armature doing the inducing, no being induced, so it might not be an armature.
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Old 12-04-2011, 05:25 PM
  #18  
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Mark, please, for the love of God, take your pedantic distractions elsewhere. I'm interested in making sure this alternator works for a hi load, low rpm street application, not underdriving it for racing, nor arguing about whether one could turn an alternator into an electric motor.

Go solve this problem, would ya?

https://rennlist.com/forums/off-topi...belt-pocb.html
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Old 12-04-2011, 05:48 PM
  #19  
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Originally Posted by Rob Edwards View Post
Mark, please, for the love of God, take your pedantic distractions elsewhere. I'm interested in making sure this alternator works for a hi load, low rpm street application, not underdriving it for racing, nor arguing about whether one could turn an alternator into an electric motor.

Go solve this problem, would ya?

https://rennlist.com/forums/off-topi...belt-pocb.html
Hey, i said what the solution might have been, a new rotor (i called it amachure because it had wires and an commutator on it). I was corrected, and it just so happens the armature is fixed and is called a stator. (symantics)

so,if the alternator is broke, its usually a broken winding or damaged or worn commutator on the rotor. if not, the regulator parts.

didnt mean to dirty this so clean discussion. read my first post.
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Old 12-04-2011, 11:10 PM
  #20  
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Originally Posted by Rob Edwards View Post
Mark, please, for the love of God, take your pedantic distractions elsewhere. I'm interested in making sure this alternator works for a hi load, low rpm street application, not underdriving it for racing, nor arguing about whether one could turn an alternator into an electric motor.

Go solve this problem, would ya?

https://rennlist.com/forums/off-topi...belt-pocb.html

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Old 12-04-2011, 11:15 PM
  #21  
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Originally Posted by Rob Edwards View Post
No problem with the alternator, it's a rebuilt unit (not sure when but there's a rebuilder decal on it) that seems to be in very good shape.

The only reason I opened it up and started asking dumb questions is because it is going to go back into Dan Hebert's Turquoise '91 S4, that will go back into service in Phoenix, and will thus be subjected to headlights/A/C/carputer/stereo on while idling in traffic in 100o+ heat, so I just want to make sure it's functioning as well as possible. Dunno how well it works, as the car's been apart for 2+ years now.

Looking back through the records, Kie bought the Turquoise car in January of 2007, at which point it had front end damage and 91,000 miles. During his ownership he replaced the alternator, then sold the car to Dan in October 2009 with 99,000 miles on it.

So the 'rebuilt' alternator from Kie's ownership has no more than 8000 miles on it, which is consistent with its appearance and good-sounding and -feeling bearings. But no way did they replace the voltage regulator given how badly its brushes are worn. And that shouldn't be surprising given that a new VR is $60-70...

So I think that this alternator is fine, but the question is whether it would benefit from a new VR- I doubt it makes any performance difference (at least 'til the brushes wear away and destroy the slip rings) but hell, maybe as the brushes wear the spring pressure pushing them on the slip rings decreases and the contact isn't as solid? I have no idea, hence putting it out there in front of more-talented-than-mine eyes. I have no idea what the critical determinants of alternator current output vs. rpm are, and how the 'age' of various components in an alternator affect this. Just trying to learn.
I'd be very stressed driving in those conditions with an perfectly working S4 alternator with those draws. Maybe let this one be and make sure he gets a very good long-pull battery like a yellow top.
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Old 12-05-2011, 03:52 PM
  #22  
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Originally Posted by Rob Edwards View Post
... I'm interested in making sure this alternator works for a hi load, low rpm street application, not underdriving it for racing,...
Want to spin your alternator faster at a lower motor RPM?

In 1990 Porsche changed the crank pulley P/N 928 102 139 12 (larger than the std. -11 pulley) and the alternator fan to a die cast to handle the higher RPMs.

I ordered mine from 928 Int. today. Tom said they only have one or two left. Being Porsche only did this for the 928 MY 1990, I'd say they are going to be considered rare as hens teeth
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Old 12-05-2011, 04:43 PM
  #23  
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Very interesting idea, but at least in PET the -11 pulley goes from 1985 up to the 1990 automatic (M28.42) engine engine 81L 51762. No idea what's on a '90 5-speed, or '91 for that matter, but it looks like all GTS engines got the -12 pulley. So hopefully they're not as rare as '90 only?
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Old 12-05-2011, 04:57 PM
  #24  
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From what I read it was for 1990 S4 only due to the lower idle speed than the 1990 GT. I donĺt have time to look today, but check and see if the GTS idle is closer to the S4 or GT.

When doing some early research on this, I seem to remember that the PET listed both the -11 and the -12 for the GTS models.

But that was some time ago and my memory of this could be off.

Last edited by T_MaX; 12-06-2011 at 07:21 AM.
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Old 12-05-2011, 05:58 PM
  #25  
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Originally Posted by Rob Edwards View Post
So the 'rebuilt' alternator from Kie's ownership has no more than 8000 miles on it, which is consistent with its appearance and good-sounding and -feeling bearings. But no way did they replace the voltage regulator given how badly its brushes are worn. And that shouldn't be surprising given that a new VR is $60-70...

So I think that this alternator is fine, but the question is whether it would benefit from a new VR- I doubt it makes any performance difference (at least 'til the brushes wear away and destroy the slip rings) but hell, maybe as the brushes wear the spring pressure pushing them on the slip rings decreases and the contact isn't as solid? I have no idea, hence putting it out there in front of more-talented-than-mine eyes. I have no idea what the critical determinants of alternator current output vs. rpm are, and how the 'age' of various components in an alternator affect this. Just trying to learn.
You're right. Most rebuilders don't replace the VR and I think that's a bull**** way to cut corners and save money. On virtually every alternator designed in the past 35-40 years the VR is clearly designed to be replaced. They're not designed to be serviced. VRs are a rip off. I won't dispute that. But then again, so are most rebuilt alternators, especially when you consider that most probably contain maybe $25-$30 in new parts, and less than an hour of labor to rebuild.

Whether brand new, or heavily worn, the brushes don't put a lot of pressure on the slip rings, but the pressure does remain fairly constant regardless of brush wear. Even if they wore out completely, their retainers probably wouldn't cause a devastating amount of damage.

What I would do if I was in your position is throw in the new regulator, put it on my car, and see what it does by driving with it for a few days. A while ago, I put one of the cheap Kaehler brand regulators on my '85. It wasn't an exact fit and the voltage was all over the place. I don't know if the problem was the regulator or the alternator. I then opted to replace the alternator. I suppose the rebuilt was marginally better then the original. If that's a Bosch VR, I'd see what it does. But the only way to find out is to test it.
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Old 12-05-2011, 06:34 PM
  #26  
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FWIW I would suggest to use a new VR from Bosch,
in the past swapping the less expensive brand X parts only made it necessary to then remove the rear cover and swap in a new Bosch VR.

The other option is to simply replace the brushes though they seem to be very difficult to find, you might have a good regulator with worn brushes .
This repair seems to also be a good solution
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Old 12-05-2011, 07:18 PM
  #27  
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Yeah, the VR I installed is a genuine Bosch VR from 928Intl (928 603 142 00). I bought one from Wagner (a W080-05, FWIW) for 19.95 but was not made warm and fuzzy by its construction. I also have a bunch of brushes from Wagner as well. (for the record they're Wagner W030-02, listed as Bosch alternator brush, 4.9 x 7.9 x 19 mm length, 60 mm LL. 12V, for 28 mm slip ring, insulated) but haven't disassembled enough to see whether the 'old' ones got replaced in the rebuild

Am working on a lead to have the alternator rewound for higher output. Not sure whether anything will come of it, will report back.
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Old 12-05-2011, 07:43 PM
  #28  
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I would see what it does with a brand new VR before doing much of anything else.
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Old 01-03-2012, 02:12 AM
  #29  
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Another day, another voltage regulator. Here's what I think is the original VR out of my '93 GTS, 105K miles on it. Brushes are in bad shape. Somehow I was unable to get any resistance measurement across the pair of brushes.



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Old 01-14-2012, 09:57 PM
  #30  
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Rob
any news of your alternator quest
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