Author Topic: Alternator failure (Read 6767 times)

dark_islight · « **on:** November 08, 2008, 04:31:46 PM »

Last year my alternator decided to give up the ghost. There was little or no warning just everything started to go dim until the car stalled out and rolled to a halt.:mad:

Today almost a year later I was cleaning out the garage and found that old alternator so I removed the regulator/brush assembly and this is what I found.

As you can see from the images the upper brush is worn to limits and the lower brush has 50% more material still left. I suppose the upper brush lost its contact and therefore failed to charge the battery.

I read somewhere on the net there is a $8.95 fix for the worn brushes by using power tool replacement brushes sanded down to the proper size and resoldered into place.

Sounds like a future project.:eek:

///m42 sport · « **Reply #1 on:** November 25, 2008, 06:30:37 PM »

I second everyone checking their voltage regulator. Thats what left me stranded out in the cold.

http://m42club.com/forums/showthread.php?t=7320

doitover · « **Reply #2 on:** November 26, 2008, 08:23:39 AM »

Thanks for the post, I didn't know any alternators had those as servicable parts.

That whole assembly can be gotten from Pelican Parts for $26. Probably worth the extra money to not have to mess with the sanding and soldering.

bmwman91 · « **Reply #3 on:** November 28, 2008, 11:56:06 PM »

Yeah, that can be a pain. Always likes to go at inopportune times. Definitely DIY repairable, either McGuyver style, or with a new replacement unit. The rectification diodes inside like to crap out, too and I have had mine rebuilt & cleaned up for $100. Good as new!

///m42 sport · « **Reply #4 on:** November 30, 2008, 02:54:36 PM »

what are the rectification diodes? They just need to be cleaned out?

///m42 sport · « **Reply #5 on:** November 30, 2008, 03:00:28 PM »

I was wondering what other cars with bosch alternators have the same voltage regulator. I was just checking on a 98 cabriolet bosch which was priced at $60 on pelican yet looks exactly the same as the regulator on my 91 318is bosch unit. Maybe there are cheaper regulators based on the car?

tjts1 · « **Reply #6 on:** November 30, 2008, 03:28:52 PM »

Quote from: ///m42 sport;61977

I was wondering what other cars with bosch alternators have the same voltage regulator. I was just checking on a 98 cabriolet bosch which was priced at $60 on pelican yet looks exactly the same as the regulator on my 91 318is bosch unit. Maybe there are cheaper regulators based on the car?

I installed a voltage regulator which was originally meant for my GFs 89 volvo 240 on my M42. It was identical and it works great. $23
http://www.fcpgroton.com/product-exec/product_id/17878/nm/1985_1993_Volvo_240_Aftermarket_Voltage_Regulator/category_id/112

With a little work im sure you'll find an even cheaper one.

Cobra Jet · « **Reply #7 on:** January 08, 2009, 10:44:59 AM »

Yep, 99% of the time, if the alternator has not seized internally, the quick fix to a "dead" or non-charging alt is replacing the voltage regulator... Most new voltage regulators do come with new brushes, while sometimes you can find the brushes separately, for the price of a new regulator w/ brushes, it's not worth the time or $$$ keeping the old reg & just installing new brushes. This is at most a 30-40 minute repair, depending on your repair skills & tool availability...

Most shops will try to get the owner to buy a new alternator - after all, it's more $$$$ for them - when in fact the only issue is a $20-$50 voltage regulator that has beat/worn out brushes... Those owners that don't know about just replacing the volt reg will get hit with a nice shop bill (considering most new alternator range from $150-$300+...), excluding the labor charges...