Spun

Well, my AC is fixed, but my alternator is charging at a reduced level (around 12.7 vs mid to high 13s). Recommendation from the auto part place is to replace. The local parts place can pick up an aftermarket for $120ish and 928 has rebuilts for $200ish.

I have read through the other Alternator posts and decided I would ask for the current thoughts for replacing the stock 1989 stock S4 Alternator.

Thoughts and recommendations?

Thank you folks... and any way to make this job easier than harder I am all ears!

Bilal928S4

I have heard that the alternator itself is very robust. The thing that goes bad is the brushes wear out. People have recommended just replacing that part. I have seen it on eBay and other places for less than 20 bucks. Might be an economical alternative worth a shot. Sorry, but I personally do not have any experience with this replacement.

ammonman

Have you taken the alternator out and had it bench tested? Is the voltage consistently low or does it change with electrical load? IF it changes with load see if you can determine which load causes the voltage drop and then start checking the electrical connections to that system. Often times dirty/corroded connections are at fault.

Mike

Bill Ball

I would look at the brushes first. The brush and regulator unit is inexpensive and very easy to replace.

http://www.mailordercentral.com/928i...603%20142%2000

karl ruiter

I hope you are not getting your voltage numbers off the gauge in the pod. It is never accurate, and turning the AC on makes its reported value plunge. Unless the belt is slipping I think the alternator itself would be pretty binary: works or does not work.

When I have problems with electrical parts I always prefer to take mine to an auto electrical shop and have them rebuilt. That way you know the history of the part, you know it will fit perfectly, and I think that when the rebuilder actually meets the customer they do a better job than if they are just going through a pallet of parts to rebuild and send to O 'reilly or Napa.

Spun

O'Reily it was... The did a load test from the battery when I cranked it up and let it run. The AC was running.

It was odd. I dropped off the car Tuesday night. Wed they said the battery was dead, or almost and the alarm was just quietly buzzing.

The said the charged it, then worked on it all day and then had to again. My thoughts were they left something open and with the doors (most likely) open all day, it drained.

I am going to wait for the problem to happen to me before I replace anything... but here in the dessert batteries do go out like a switch or you can loose cells ... but we shall see and I will report back.

Landseer

You are letting a non-928 shop work on 928 electrical questions?
I'd rethink that. It takes weeks of exploration with wiring diagrams in-hand to figure out what needs to be touched and what needs to be left alone.

As the cars age they get electrical draws that require about 2 or 3 days of intense cleaning of contacts to hunt down and fix. You want to do that yourself or have a 928 specific shop do it, really. There's a list of stuff.

The alternators can be fixed with parts, suggested above. But if you go instead with a rebuild, buy only a Bosch factory rebuild because they actually remanufacture the armature/stator apparently. Other rebuilders do not.

This is what I've done on the Bosch that failed on our 86. Slight tap would get more voltage from it --- a few times, then it failed and was replaced with Bosch factory rebuilt unit bought via Advance Auto.

I

Alan

I too would start with the simple cheap stuff - first check the tension on the belt - it needs to be super tight - did it get removed for the AC work? Then consisder the regulator replacement - you can easily do it yourself.

Is the 12.7v at idle? is it better at > 2Krpm?

I'd also consider getting the battery fully checked out - it could be the culprit if its failing...

Alan

Spun

God no ... I will do all the work myself. I just had them test the battery and alternator while I was having them replace the other batter that I got from the 18 months ago that crapped out... figured it would not hurt. I will come here first for fix/replace/repair advice

agreed. I am going to let the car sit tonight with the alarm on and see if it drains the battery. I have not cranked it today, but that is what I am up to next.... I do know batteries go quick around here, but I believe that the battery and alt are not that old (going through the records on the vehicle in a few min to verify).

I do not plan to be in a rush to do anything on this baby... no need to jump in and step on myself. I sort of did that with the Ford Motor Mounts, but the will be fine. I will fix them with the Volvo once the rack needs fixing... which will come at some point... on a good note, the oil pan gasket is sealed like a champ

928mac

OK here is my 2 cents

-Most of the problems with the 928 electrical are caused by dirty grounds.
As Karl said, the pod gauge is not a good value.

-Check the votage at the battery before you start it, then start it and rev it up and then check voltage at the bat and at the alt.

-The bat must be good and be charged to give a true reading.

If it is low, then here are your choices.

1)repair it yourself as above (I chose not to)
2)replace it with the AC delco (think its a 82 camaro) alt.
3)replace it with the same or have it rebuilt
(I chose not to because the voltage is always low on these bosh alt.)
and I wanted to install a bigger stereo, amp and sub.

4)I paid more then I should have and put in the 928MS 200 amp Alt.
I like the power and voltage that it supplies, but the brackets suck and I stold some of my air pump bracket parts to make it work.
-I also installed the optimun deep cycle battery because our cars with the old circuits tend to leak power.
(My drain was the rear defog relay which I removed)

so the choice is yours.

research the GM delco Alt. but I could not find the one that fit in the S4.

Good Luck and let us know how it turns out.
Brad
928 owners club

Spun

Hmm... I might start looking for this just so I can have it as a spare. Does the end product fit without issue (I assume you have to swap the pulley)?

928mac

Delco Alt. do not come with a pulley. I believe there are a few threads on the swap.

Landseer

????
Delco works for 16V.
Nobody has found an equivalent for the 32V.

Several have applied the Delco to the 32V by transferring the whole power steering pump / alternator bracket assy from an earlier car.

I run Delco on 2 16v cars. Only because it was cheap and quick at the time for replacing the ParisRhone OEM unit, which has a design that begs for destruction when foreign matter enters the air duct (shells ripped the diodes out of both of them). Advice to 16V rescuers --- vac the duct before you start the car.

If you have to work on the alternator, follow Bill ***** advice or buy a Bosch-factory rebuilt or new unit. I bought a bosch rebuilt one last year for about $175 delivered to my local advance auto in full bosch wrapper / package.

But the best way to begin is complete electrical contact cleaning. Really worth the effort in reliability and peace of mind.
Am not a pro, but have been involved on 8 of these 928s and a handful of 944s now --- its a beautiful thing. Beautiful because owners dump their cars cheap because they can't conceptualize that grounds and contacts could cause such havoc and don't know where to begin! Then we buy them.

Spun

This is my first project once the kids head home next week. I have seen/read/heard this is a 3 day job, so I going to probably take it in stages... After a quick search on here and finding these two links I can see why 3 days could be used:

• http://members.rennlist.com/jerdmann/electrical.htm
• https://rennlist.com/forums/2220328-post33.html

At least I know what to do with my spare time

Landseer

Saves time in the not-so-long run.

Here's one for an earlier car, slightly different ground points, wordy, sometimes tangential.
But it shows the approach -- http://forums.pelicanparts.com/porsc...-16v-euro.html