Low voltage at battery, new alternator time?

[perry roubay]

Hi,

I recently upgraded from a 991 to an 82 SC. So the car is "new" to me. A couple days ago the alternator light came on mid drive. It was a little sporadic, off at higher RPM , on at lower RPM, fading in and out, bright at high RPM, all over the place....

The belt was recently replaced so I checked the tension and it seemed a little loose. I moved a few spacers to tighten it up and it didn't make a difference. The battery, with the engine off, reads 12.4 - 12.5 volts.*When I check the voltage at the battery with the engine running it's 11.4, when I turn on the lights, the radio, the fan at the highest speed it's under 11 volts and continues to drop.

Long story long, does it sound like the alternator is the issue or is it possibly something else. Just wanted to double check before I spent the $$ for an alternator.

Thanks in advance.

[911obgyn]

Regulator, alternator, connections at the battery, starter, alternator. Have the alternator checked at a rebuild shop. Then have them rebuild it. If its bad. Meanwhile check grounds. At the battery, at the transmission to chassis, and from the alternator to the block while you have it out. And check the wire to the starter and the wire from the starter to the battery.

[MBAtarga]

I'd suspect regulator. Symptoms my SC had included varying headlight brightness as well.

[perry roubay]

Thanks, I'll give those things a look

[rattlsnak]

The newer alternators have the regulator built in to them..

[John W.]

I recently had my 3.2 rebuilt. New brushes, bearings and regulator cost $105 and fixed my problem.

[pmax]

The VR can be replaced by itself as well.

[perry roubay]

Thanks for all of the info.

Question: if the regulator was bad would the voltage at the battery be low, 10-11 volts? Everything I've read about regulator issues involves high voltage that wrecks the battery.

[GH85Carrera]

First thing to check with a battery charge issue is always the battery ground and positive connection. Remove the connections. clean them.

If that does not do it, remove the alternator, and take it to a local rebuild shop. Tell them to please use NOT Chinese made bearings, and do a full rebuild. Take pictures of all the connections for the alternator to aid in reassembly.

[cmcfaul]

Just replaced mine. $200 through Advanced Auto. Looks brand new, Bosch unit replaced the Velaro Alt that was in there. Two year warrantee. Hard to beat.

Chris
89 Carrera

[911pcars]

Perform the above in a logical progression. E.g. Do not buy a new/rebuilt alternator first, then check the battery cable connections. Buying new stuff is nice and all, but simple fixes can get expensive.

Sherwood

[perry roubay]

So I checked the ground at the battery and transmission and then cleaned up the battery cable connections. They looked good, the ground was good. Figured I'd start it and see if any of that made a difference... car wouldn't even turn over, battery now reads a little less than 12V.

Decided to pull the alternator while the battery is on the charger and have it tested. Well, the outer race of the bearing that is opposite the fan is very loose inside the alternator. Loose enough that you can make the bearing move inside the bearing bore with the shaft. I would guess it moves 2-3 mm side to side. You can see how far in this picture. I assume that isn't normal....?? There were a few pieces of plastic inside the air flow guide that look like they might have been a cover for the bearing.




Didn't bother taking it to the shop just yet.

[Joe Bob]

My experience.....

Test the battery at the terminals. Engine not running, you should see 12.8+ volts
If under 12, charge battery. If the Battery can't get over 12.5 have it tested or consider replacement if over 5 years old.

Running at idle all accessories off. 12.5 ish. If lower rev motor. If no change, start check grounds and other connections. Also check the battery light is operational. It is part of the charging circuit.

Check cables for cracks in the insulation and corrosion UNDER the terminal connections. You may have to remove and retighten them. If the surfaces are dark, take emery paper to the connections and the mating surface. Shiny is good.

If you still have low voltage output when testing at the terminals with engine running, get it tested. Low voltage CAN either be the regulator OR the alt or both...since most all alts are now combined units, replacement time.

IMHO the Autozone, Pep Boys and other auto parts stores sell cheap China remans. They offer life warranties in most cases but no labor...some are now limiting warranties to 5 years.

If you have ever done and r&r on an alternator, it is time consuming. No cost if you DIY. You pay a wrench $150/hr. Prolly two hour minimum. A high percentage of starters and alts fail out of the box. They only replace dead parts, sketchy is OK in their book, not mine.

If you can find an old school local rebuilder do so. The problem is decent parts. If he knows his trade, he still has sources. Likely no installation services. But you know who to see if it fails. IT WILL cost you more for the rebuild. Welcome to the Porsche tax.

Post your location, you might get a volunteer to help. Make a new Porsche friend.

Good luck.

[Joe Bob]

Sorry your post was not up until I was done with mine. Bearings that are loose aren't good.

[perry roubay]

Joe Bob, thanks for the reply. I figured as much with the bearing that loose. When I realized the dried and broken pieces of plastic appeared to be a bearing cover I guessed it was probably done.

[nzrobinz]

Had my alternator rebuilt last year - it had the same symptoms - cost around US$100.00 - this was a 78 unit so it had done well

[mysocal911]

Originally Posted by cmcfaul

Just replaced mine. $200 through Advanced Auto. Looks brand new, Bosch unit replaced the Velaro Alt that was in there. Two year warrantee. Hard to beat.

Chris
89 Carrera

Bosch never made an alternator for the 911 3.2. Most likely it's a Valeo alt in a Bosch box.

[GH85Carrera]

In my experience with alternators, the parts store units are "rebuilt" at some big warehouse in a third world country, and very hit or miss in quality.

Go find the local alternator and starter shop in your hometown. They have likely been in business many years, and will rebuild it properly. Demand no Chinesium bearings, and have them do a full rebuild, bearings, and brushes and check the diodes and any other parts. It will be 1/2 the cost of the parts store questionable alternator. And it will certainly have the wires in the right place. You will keep the money in your town, and help that local shop stay in business.

[yelcab1]

Where do you get your alternators rebuilt for $100, with no Chinese bearings, no less?

[Flojo]

Originally Posted by yelcab1

Where do you get your alternators rebuilt for $100, with no Chinese bearings, no less?

I refurbed mine myself.
Test-run and ports check at an automotive workshop EUR 15,-
Two new SKF bearings purchased at a German online shop EUR 25,-
New Regulator and carbon stick unit EUR 32,-

Deduce EUR 10,- parts shipping costs a shop won't charge, then the difference to 100 is wage I guess.
Sounds fair.