jeff spahn

I took my Bosch alternator out during my engine removal and repair. I installed a new voltage regulator that I got from Roger at 928sRus. While engine was out I took it to an auto electric shop and had them test it. Told me it works perfectly. My voltage now reads 14.1 at the charge post and doesn't drop below 13.6 with the front and rear air on.
What a difference! Lights don't dim, very nice to have it working perfectly.
Now with all the grounds cleaned, all connections secure I am hopefully away from electrical gremlins for a long while.

85euro928

Jeff,
Anything special required to change out the regulator? Have any pics? My alternators laying on the floor waiting to go back in; maybe this is another WYIT for me?

Bertrand Daoust

+1.
I guess that's something I will have to do as the alternator is not very "strong" when warm.
As I'm not a mecanic and never done that, any tips and pics would be very appreciated.

Thank you.

Mrmerlin

the trick with the regulators is to buy Bosch replacement parts.

yes you might find a less expensive regulator but it isnt built to the same standard that the Bosch parts are and usually the alternator wont work as well as it should or last as long as it should.

Be careful with re builders as well as they sometimes also go the cheap replacement parts route

jeff spahn

Super easy. With the alternator out of the car already you just take out the two screws holding the regulator in and swap it. That easy.

tmpusfugit

You may want to keep in mind there are many things in an alternator that can and do fail besides the regulator. The regulator itself has the brush(s) attached, and the brush(s) ride on copper strips called for lack of a better word commutator strips or rings. They wear, particularly if there is no shroud on the alternator and no pan on the car (both serve to keep grit and other road debris out of the alternator) Replacing the alternator regulator gives you new brushes but does nothing for the rings...and if they are badly worn, you will still have problems. Also, there are from 6 to 15 diodes in alternator (the number varies depending on who made the alternator and when it was made) If any of these diodes fail, your output will not meet specs, and voltage will be too low in most cases. Then there are the bearings, also subjected to road grit and dirt. They seldom fail, but it does happen. Finally, the windings of the alternator can also open or short...neither happens often, but it does happen.....

I have paid for a couple of "rebuilds" that were not rebuilds....worn brushes, worn out commutator rings...but cosmetically clean…they didn’t last long. Also, the rebuilts that are now carried by the usual suspects (Pep Boys, Advanced Auto etc.) for the pre 32 valve engines are not “correct” and will not accept the fan shroud and the like….

blown 87

Times eleven billion

WallyP

On the other hand...

If you have a local rebuilder who has been in business for some time, it is worth talking to them. It is amazing how many special "problem solving" products a rebuilder has access to. My rebuilder told me that there were several (perhaps six - don't really remember) different regulators available for the 928 alternator. One of the specs that is different is temperature compensation.

As I understand it, the temperature compensation is intended to compensate for two different factors, alternator output that varies with temperature, and battery performance that varies with temperature. Lead/acid batteries are electrochemical devices, and the charge performance varies quite a bit with the battery temperature. Since many cars have the battery in the engine compartment, it will be hotter than our batteries. The "standard" temp compensation is for the battery in the engine compartment, which means that the charging rate is reduced as the regulator gets hot. (Another good reason for having the alternator cowl and cooling hose in good shape.) Bill said that he could install a regulator with less temperature compensation and improve summer performance of the charging system.

Bertrand Daoust

Very interesting Wally.
Thank you very mutch.
Bill, would you have some info on this please?

JHowell37

I tried one of the cheap Huco brand regulators. Voltage was all over the place. I changed it out with less than 50 miles on it. I didn't want to damage anything in the car.

S4ordie

Or, "Ninety one thousand one hundred". Plus points if you can recall this reference...

Bill Ball

I rebuilt my alternator when it started to make some obvious bad bearing noise. It needed almost everything from the regulator and brushes to the bearings and a plastic bearing tolerance ring, and the copper slip ring. To figure out which parts I needed to order, I found Wagner Alternator Products catalogue here:
http://www.wagneralt.com/visions/
and searched for 92860301101, the alternator for my year (89). This cross-references to Bosch 0-120-468-004 and displays that component parts list. It shows Wagner part numbers and from there you can find the parts with a whole bunch of cross reference numbers in their component catalogues here:
http://www.wagneralt.com/catalog/books/default.asp
I ordered the parts from Nations Starter & Alternator.
http://www.nationsautoelectric.com/index.html

The rebuild was not too bad. I used this write-up as a guide:
http://www.rangerovers.net/repairdet...haltrepair.htm

Bertrand Daoust

Thank you Bill.

Danieldd

Very timely article. My alternator was pushing over 19V. I wished I had the foresight to check to see if there was any AC on the line - as it may have been what fried my ignition coil.

Anyway, I took the alternator down to two different parts houses to have it tested. At one place, the alternator kept shutting down their machine and they couldn't figure out why. The other shop confirmed that it was bad. I also called a local rebuilder. As soon as I told them it was a Bosch alternator for a Porsche, suddenly the cost to rebuild it was $200.00.

I've decided to do it myself and with Bill's reply - just what I need. I have the same alternator. My bearings appear to be okay, but I'm certainly going to be replacing the regulator/brushes and diode assembly. Oh, I need new slip rings too....