80 SC alternator- correct part? Solved
 

The replacement alternator from the salvage yard was as dead as the one I initially took out. Got a rebuilt alternator from Franz the Porsche mechanic, installed it, and all is well!

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All,

I just received my replacement alternator from my not-very-local Porsche dismantler, and it seems that it doesn't match:confused:. What do I have (on the right)? What did I receive (on the left)? What's my best way forward?

From the front
http://forums.pelicanparts.com/uploa...1356951406.jpg

From the back. Note I have 5 wires (4 lugs and a clip) on my car. The new alternator has but 3 lugs.

keyhttp://forums.pelicanparts.com/uploa...1356951286.jpg

Finally the shafts are different. Different radius on the threaded part, and different threads. Also, mine has a key on the shaft and the new one doesn't- is the key transferable, or not? If so, how?

http://forums.pelicanparts.com/uploa...1356951747.jpg

Thanks,

What you have is the 82 and later alternator with the on board regulator. The early alternator has 4 wires connected on the back. On your harness, tape off the black wire and use the other 3 on the update. The nut for the alternator is 24mm with coarse threads.
The keyway should be the same but I cant find it in the PET. The key should just peel out with needle nose or a small screwdriver.
Bruce

Plus you may have to notch out the air diverter to fit around the regulator.

Good news: I test-fit the air diverter and it would not need to be modified.

Qestionable news: The alternator has 3-4mm of end play in the shaft. Is that normal? The old one has it too, but I figured that was part of what was wrong with it.

And finally, I don't have 4 wires, but 5.
1. clump of small brown wires on an eyelet
2. large brown wire on an eyelet
3. blue wire on an eyelet
4. 2x red wire on an eyelet
5. black wire on a female spade connector.

http://forums.pelicanparts.com/uploa...1356962773.jpg

Is it better to go with this '82 and newer unit, or match what was in the car originally?

1 and 2 go onto the ground lug, the black one(5) is not used with an internal regulator and should be cut or taped off, 4 (two red ones) go to the largest bolt (+), blue wire is the exciter. IIRC, the top stud is the blue wire, the largest is positive and the remaining one is ground. Do a search on "internal regulator" and you'll get a good chart.

End play
 

OK, so it can work and I know how. The only other question- what about the end play? Is 3-4 mm of end play normal and OK?

OK, I don't entirely know how. What about the key in the shaft? I gave it some grudging taps with a hammer and screwdriver, but it doesn't seem inclined to fly right out.

Once it does fly right out, how do I press it into the new one?

There is a pin dot on the key so it doesnt remove easily and wont fall out while installing fan.
Bruce

That doesn't even look like the same alternator. I had one recently rebuilt (similiar to your old one). Link here for the adventures....
http://forums.pelicanparts.com/porsche-911-technical-forum/688123-another-alternator-charging-light-bulb-question.html
I don't think that you can even use the same fan since the shaft diameter is different, (so your'll need to come up with a new fan that fits in the old shroud....) which means a new nut on the end too.

Given the variability of the alterntors for the SC, and the difficulty tracking one down that would fit in for sure, I opted to just go for a rebuild of the one I had. I know that one fits!

And Bruce's comments about the pin dot on the key is right on... I didn't realize this and filed mine off so it was more easily removable. Not the end of the world, but more exiting on the reinstall!

J

I would find a competent re-builder for the original unit.

Open Question: End play
 

And now I know what a pin dot is. Thanks Bruce- I got it out.

I had read the thread you mentioned. Thanks. The unthreaded part of the alternator shafts are the same for the two alternators, so the fan is OK. New nut and spacers came with the new alternator.

Unfortunately, the old unit had no labels or identifying information on it whatsoever. I'm not sure which continent it came from, or which sweatshop it came out of. The Bosch people wouldn't touch it, so that closed off that avenue.

I still don't know about my end play. The shaft can move in or out of the alternator 3-4mm. When I push it in all the way, it will no longer turn, but in an intermediate or all-the-way-out condition it spins freely. Is this normal?

May want to review this service bulletin too.

http://www.pelicanparts.com/techarticles/911_alt_replace/Alternator.pdf

They don't have old school rebuild shops in Germany? That sucks.....not very green to have to buy new everytime a generator/alternator/electric motor goes kaput....

Your old one looks a lot like my Marchal, just missing the rear cover.

http://forums.pelicanparts.com/uploa...1357024629.jpg

Dennis,

You're right- mine looks just like yours. Does your Marchal have any markings on it other than the plastic cap? I found bits of the cap on top of the motor when I pulled the alternator.

No other markings other than what the cap has. That picture is a year old and I didn't write down what the cap said.
55 amps is all I really remember.
maybe someone else has the info written down or has a picture.
Here's a good rebuild thread:
http://forums.pelicanparts.com/porsche-911-technical-forum/629232-can-sev-marchal-alternator-aka-mr-sparky-repaired.html

The current state of play
 

• Plastic trimmed from back of internal voltage regulator so the shroud fits
• Black wire taped off
• Wires cleaned with sandpaper to a beautiful coppery shine
• Brown wires attached to the small lug, red wire to the large lug, and blue wire to the top
• Alternator reinstalled, fan belt set to proper tension. Not a single nut or washer dropped into the dark recesses of the engine!

When I turned the key, I got a dim glow in the OXS and generator lamps, RPM independent. Battery shows 11.7 volts when running, also RPM independent.

I disconnected the external voltage regulator, hoping that might help. Now the generator lamp is out under all circumstances (key off/on or engine on). Voltage at the battery is 11.7 when engine is running, and 11.4 with all the accessories on. Bentley says this means the alternator is bad. I'd really rather that not be. Is there something else I should try before I pull this all apart again? :o

Many thanks.


The good news- while the car was sitting still waiting for the alternator, I did the tensioner update, and with setting the timing tonight that job is successfully finished! Well, except for those dastardly paper hoses that I need to replace....

I'm really surprised more people do not recognize that you always save and rebuild your old alternator, even when getting a "new/different" one. A rebuilt alternator is always worth good money - more than the core difference you would get on trade in.

If you can install an alternator of questionable road worthiness than you will quickly be able to pull it all apart and install your original, rebuilt unit that you know will work.

Any alternator can be rebuilt - many shops across Europe can perform this service for you. I rebuilt the Valeo I found in my '78 for $125.00 USD just FYI.

Check that service bulletin I posted above. There is mention about installing a resistor if the charge light does not go out.

Two problems- the light doesn't even come ON, and there's no charging happening. A resistor is probably not my solution at this point.

I'm learning as I go. I assumed the completely unmarked alternator that came out was a far-Eastern knockoff, but through what I've learned on this thread I'm pretty sure it's an OE Marchal, so may be worth rebuilding. If the "new" one in there is no good, then Ill probably be back to rebuilding what I have.