New Bosch brushes used in 103 motors are 1/2 inch long when new.

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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

I'd replace the voltage reg/brushes first as it is cheap and easy. It wouldn't hurt to get the alternator's output tested once you've done this though, to make sure it is functioning properly.

I recently had to replace my ailing alternator - I replaced the brushes and it seemed to work but the battery gradually died. Tested it and it was only putting out 35-40A. Only way to test the current output is at a tech's or with a good pair of field clamps. Getting just a voltage reading with a multimeter on the battery isn't really enough to fully troubleshoot the alternator.

If you do replace the alternator, ditch the crappy 70A and replace it with the newer 80A or higher Bosch alternator. I got the 80A and it is MUCH better than the stock 70A - no more dimming lights ever!

__________________
Chris
2007 E550 4Matic - 61,000 Km - Iridium Silver, black leather, Sport package, Premium 2 package
2007 GL450 4Matic - 62,000 Km - Obsidian Black Metallic, black leather, all options
1998 E430 - sold
1989 300E - 333,000 Km - sold
1977 280E - sold
1971 250 - retired

"And a frign hat. They gave me a hat at the annual benefits meeting. I said. how does this benefit me. I dont have anything from the company.. So they gave me a hat." - TheDon

Man, I just had my brushes out to inspect them... they're plenty long, and really hard to get back in! Hahah...

Also, A&F Parts in Oakland wanted to charge me $75 for a new regulator! WTF? I guess either the loose battery terminal clamps are responsible for the no-charging thing, or I need a new alternator, 'cause the brushes look fine. (Any way to test them, by the way?)

Cheers!
Ash

__________________
Ash Peltier - tools, truck, tales
---------510-331-4118-----------
1982 240D - (272,000)
1998 Honda VTR1000F(RT) Superhawk Freeway (58,000) "Madrid"
1996 Toyota T100 4x4 (84,000) "Mary Kay"

Just because the brushes look good doen't mean that the voltage regulator circuit is good.

There are plenty of places (Autozone, Sears..) that will check it for free if you don't have a meter.

Took the whole alt into the alternator shop and they found the regulator to be bad. $20 later, and super clean from their special cleaning wheel, and I'm back in business!

$75 for a regulator...

Ash

__________________
Ash Peltier - tools, truck, tales
---------510-331-4118-----------
1982 240D - (272,000)
1998 Honda VTR1000F(RT) Superhawk Freeway (58,000) "Madrid"
1996 Toyota T100 4x4 (84,000) "Mary Kay"