Does my alternator contain parts that wear, like brushes?

[Bill Dennes]

I'm sneaking up on 90k miles and I'm curious about the alternator. Will it run until a bearing dies, or are there parts in there that will wear out?

 

Right now it makes 13.9 volts.

 

TIA

[kioolt]

Yes it does have brushes that will eventually wear out. How long it takes I don't know. I've got about 100k on the same alternator that is on an R11XXRT's on my 91 K100LT now without any problem. I did check them a couple of year ago and thought that they were good to go for quite a while longer. I believe that you have to buy the brushes and regulator together for that alternator.

[Paul Mihalka]

In theory yes, brushes and bearings wear. For my R1100RT I had a spare alternator at home I picked up from a totaled bike. Sold the bike with 170K miles on the original alternator.

[A-Red Bill]

I use the charging system on my RT hard. 92,000 miles, moto-lights on always and gerbings whenever I need it. I had the transmission out this winter anyway and bought a replacement brush regulator assembly from euromotoelectrics for $49.00. It is hard to determine brush wear but I would say that they were perhaps 40% used up. That said I feel good about it anyway. Once you get to the alternator, replacing this assembly is a piece of cake.

[duckbubbles]

I rebuilt my K-bike's alternator at something around 160,000 miles. Not that it quit working, I just decided to do it. There is a measurement you can perform on the brushes once they are removed. I think the service limit is something like 5mm. New they are around 11mm. I cleaned the rotor slip rings, installed a new brush block and bearings and ran it another 150K before I did it again.

These high output alternators seem to last quite a long time with no maintenance. Your mileage may vary.

 

Frank

[JonathanE]

The single biggest advantage of an alternator over a generator, even greater than it's non-linear voltage response, is the ability to utilize slip rings instead of a commutator. Commutators wear brushes out many, many times faster than slip rings. It has to do with voltage gradients and gaps that cause more arcing between the carbon brushes and the copper commutator. Brushes see zero voltage gradient across a slip ring, and have no comm bar gaps to arc across when making or breaking a circuit on a stator coil circuit.

 

I am pretty sure that I'll never bother changing brushes on any alternator I ever own, and I used to have a crew of eight men checking and changing brushes for a full day every week on my steel mill. They would change hundreds of brushes every week.

 

When you change brushes in an alternator, keep your electrical load minimized for several hours of use, since they must seat to the slip ring properly before they make full electrical contact. Overload them when they are only making partial contact, and they can burn the slipring, or glaze it, both of which create a resistive connection that is HOT and can melt areas of the slip ring, causing irrepairable damage.

[T__]

I'm sneaking up on 90k miles and I'm curious about the alternator. Will it run until a bearing dies, or are there parts in there that will wear out?

 

Right now it makes 13.9 volts.

 

 

TIA

 

Bill, probably the 2 biggest wearing parts in an alternator are the bearings & brushes.. The bearing wear is largely effected by drive belt tension & any dirt debris that enters the bearing area.. Age on the bearing grease, & extreme temperature over time can also have a negative effect on bearing life..

 

As far as brush wear goes, again dirt in the brush contact area can have large effect on brush/slip ring life & power washing an engine has a tendency to blow dirty water into the alternator brush zone shortening the brush life considerably..

 

The brushes on automotive type variable magnetic rotor type alternators is usually pretty good with long life the rule.. Unlike most older generators that carry all the charging output current through the brushes most modern alternators using variable strength rotors carry the full charging current directly from the non rotating stator pig tails to the rectifier/electrical load & the brushes only carry a lower current required to just energize the magnet in the rotor & make it a magnet, the brushes/slip rings don’t carry the actual charging output current load..

 

Twisty

[bmwmick]

Bill,

You can get a new regulator/brush unit for little $$.

Transpo IB385 is a direct replacement. They're $35 at your local alternator/generator/starter repair shop. They have a 14.5 volt set point vs the OEM Bosch's 14.0 volt set point.

 

I just pulled the original 32A alternator out of my '93 K1100LT and installed a 50A unit with the new IB-385 Reg/Brush unit. I removed the reg/brush asm on the old one (140K miles) and the brushes were still about 5/8" or more. I doubt you'll ever wear the brushes out. The front bearing was just slightly noisey.

 

Mick

Tucson