Charlotte944

I've been down this road before, and just today the alternator in my 951 started acting up, so I'm getting ready to do this again. I say replace the alternator.

What I've learned is that as these alternators "age", the slip rings get worn down and develope some rather nasty grooving which shortens the life span of the brushes in the voltage regulator.

Another usefull tid bit is the ageing of the varnish that covers the stator and armature windings. Over time this varnish gets "over cured" and can start to crack and flake off, leading to internal shorting.

Next are the bearings. Worn bearings place more mechanical load on the engine and drive belts which wastes power and shortens belt life.

Finally there is the diode pack. This component is what converts AC to DC. Diodes can short internally, or fail open, neither of which is a good thing.

SamGrant951

Well, I guess it also depends on how much you use your car. Mine travels about 3k miles a year. To me it wasnt worth replacing the entire alt. when it wasnt necessary yet, the $18 solution was much better.

95Juan

problem got fixed by not blasting my subwoofers everywhere i go. volts dont go above halfway between 12 and 14 anymore.

goddammit i hate electronics........

jf951

not that i can offer any help but my 89s voltage is at 12 sometimes a little higher sometimes lower does this mean that i need a new alternator? mine was replaced 70k ago. thanks

ibkevin

Install the adjustable VR as is. If the volt gage is still shy then adjust the VR up.

jf951

reply, thanks...

jf951

well driving on a crowded interstate i'm in fast lane at about 80 then merge over tothe right lane slowing to exit. an idiot who was trying to catch up to me follows me over and is inches from my rear bumper i just kept slowing down, then exit to another freeway which is flat and straight for miles but a double fine zone so i just slowed down and let him go but what else do you do if someone want's to prove that their shiny new SUV is faster and handles better than a little foreign car?
btw way anyone see that thing on tv about super speeders, ferraris, lambos and vipers weaving through traffic at triple digit speeds?

Charlotte944

Replaced the starter and alternator this weekend. Regulator brushes were worn to the limits. System voltage with no load is just a tad under 14 volts and drops to about 13 volts under "full load" (headlights, fog lights, rear defroster, wipers, vent fan on 4). Next on the list is a new battery just to make sure.

95Juan

now i'm basically at the mid-point or a little lower (never under 12, or even touching 12) all the time, no load, full load, etc. i mean, i can see it go down a tad, but it's not that big of a difference. it did shoot up to 16 once...then never again. god dammit i hate electronics........

Dash01

This happened on my Bimmer, so I just rebuilt its 140 amp alternator, for less than ~$80. I disassembled it and took it to a local auto electric shop, where they lathed the slip rings smooth and clean. They sold me a new diode plate for $36. With the alternator apart, it took the bearings to a farm implement store and got equivalent (or better) new sealed bearings for a small fraction of the price of exactly the same bearings at an auto supply store. Replaced the regulator brushes by soldering in new brushes where the old ones wore out, and bought an aftermarket regulator w/brushes as a spare/backup, for ~$12.

Works like new, because virtually all the parts that might wear out were replaced. Of course, it fits the car perfectly, unlike what one might find at Autozone, etc.. Your results may vary.

951North

Dash01,

What were your symptoms that alerted you to the rebuild? The Battery in my BMW drains periodically, the voltage output from the alt is good @13.x I fear the nature of driving habit is to blame, short trips in cold weather. The draw on the Battery is only ~60 mA when car is off... What I've ended up doing is I put the battery on a charger with a "Monitor" onces a week overnight and that helps alot.

Thanks

Jason

Sorry for the H/J, but others may find this usefull as well...

Dash01

Battery was not charging properly and the dashboard lights went out and the car barely made it back to my driveway. But, the battery was an old one, so I had it checked and it was OK. Took alternator to NAPA for bench test, and it had inadequate output. I then proceded as posted above. My reasoning was that there are only so many things that can go wrong with an alternator, windings, armature, and case not among them. That leaves regulator (very cheap). brushes (extremely cheap), bearings (pretty cheap at farm implement store), diode plate (not too bad, but sourcing scarce), and lathing slip rings (pretty cheap).