M50 Alternator (advice needed)

[Scott E]

My buddy has a 1992 325i Automatic (build date 9/91) and the alternator appears to be going bad.

Is it possible to replace the brushes and regulator? or should we replace it entire alternator.

On a good note I recently replaced my entire cooling system in my 535i M30. New radiator, radiator clips, radiator mounts, thermostat, thermostat bleed screw, water pump, belts, coolant tank, coolant cap, hoses, and BMW coolant. Parts were about $600 from BMA.

Thanks,

[ryan roopnarine]

my alternator had (obviously) had the brushes replaced in it before, and had at least 40K on it with new brushes. if you make sure there isn't excessive play in the mechanicals, yeah, go ahead and change the regulator. i'd suggest taking the regulator out and ordering it by part number from bma, instead of relying on them to match a unit up for you...here's some background
http://www.bimmer.info/forum/showthread.php?t=1222

might also consider extricating the alternator and taking it to a hard-core auto electric rebuilder (one that doesn't cater to the general public for the most part)....with parts all over the floor, grease everywhere, shelves full of used alternator parts.....i got quotes for $50 to take mine apart and replace bearings and brushes, clean up &c. &c. yeah, you can just replace the regulator.

[Tiger]

If undercharging... such as low voltage of 13.4V or lower, you can get away with just changing the brushes/regulator one time.

[Unregistered]

I replaced the bearings on mine a couple of weeks ago. Car parts places wanted ~$25 for the larger bearing, and about 1/2 that for the smaller one. I went to a farm implement place (Case, IH, Deere, etc.) and bought better bearings for 1/6 the price. Had the contact rings turned on a lathe for $10. Aftermarket regulator/brush assy. cost $13. Rebuilt the old regulator with new brushes for ~$3. Now have, practically speaking, a new alternator, plus the old regulator with new brushes as a backup. Total outlay less than $25, plus some running around.

[Scott E]

As luck would have it my friends e36 has the 105 Amp alternator. Being a holiday and in a hurry he called all over town to find a new regulator and bushes. Naturally no one carries them.

The alternator feels very tight and we removed the brushes and regulator. Part number is 1 197 311 027 and according to the BMA website it is in-stock and available. I am so grateful we pulled it out and got the exact part numbers as recommend.

I also put a full charge on his battery for good measure and cleaned the trunk out in the car. Now the spare tire and jack are in place along with the battery being strapped down correctly.

Lucky for my buddy and I BMA is less than an hour away by drive and parts arrive overnight at minimal shipping costs.

I suggested to my buddy once he installs the new brushes and regulator that he have the unit bench tested before spending the time to install it.

Thanks again for everyone's input into this matter. I will post a message and let everyone how it turns out.

[ryan roopnarine]

tell him if he doesn't want to test it off car that Autozone or Discount Auto Parts can test it on car if he likes, but it obviously isn't the same.

[Scott E]

I learned a few things that might be helpful to others.

• Remove the upper radiator hose for easy access to alternator
• Remove the air box
• The belt tensioner needs to be turned clockwise to loosen and remove the belt.
• It is best to remove the alternator and get the part numbers.
• Replacing the brushes/regulator was far cheaper than a rebuilt alternator
• When you friend says he has tools and stuff bring you own just in case unless you have seen his tools personally
• Working in the dark sucks ass...lol

Thanks again for advice everyone provided. It was most helpful.

[Unregistered]

Here's another trick: Get a cheap dental mirror to read the part number. You gotta read it backwards, but that beats taking the alternator (or whatever) off the car to read it.