From digest.v7.n14 Mon Jul 28 15:48:02 1997
From: <don.mcmahon_at_cis.state.mi.us> (Don McMahon)
Date: Mon, 28 Jul 97 9:22:32 EDT
Subject: soldered alternator pigtails

Richard Cartilege:

I recently rebuilt my alternator brushes/rectifier pack with the Bosch kit from BMW. The kit had a couple of small fittings (copper?) through which the pigtails are pulled. Sort of like:

   )__________|///////xxxxxxx-----------------       o=
          /        /      /           /             /
     brush   spring pigtail  stiff-copper-wire     fitting

     I also had problems getting the factory solder to melt with the iron. 

Having only two cars but having three sets of brushes/rectifiers I plowed ahead. First observe and remember the position of the brushes in the holders. I ground off the soldered ends, pulled the brushes and springs out and then filed down smooth the surface of the terminals where the pigtails would be soldered. Not being good at soldering, I enlisted the help of a physics lab tech. (He taught me a little trick - putting some fresh solder on a clean soldering iron tip aids immensely in heat transfer).

Using two sets of hands (could have done it with three) we threaded the first long copper wire and pigtail through the brush holder, (I believe there is a grove in the graphite brush which must be lined up) and then through the small copper fitting (bitty tube with flange on the end). The brush must be pulled through enough to seat the brush springs and yet allow enough travel in the brushes to make contact with the contacts on the armature in the alternator. This point seemed to occur when a little of the pigtail was exposed through the copper fitting.

With the brush seated in the right spot we soldered the outside of the pigtail to the outside tip of the fitting first, allowing a small amount of solder to flow down into the fitting. We then soldered the area at the base of the fitting trying to be careful not to over heat the area causing our first solder to let go. The second brush was soldered in a similar manner. The copper wire was the cut off.

The rebuilt brushes at least look as if they will work :-) I have not put them in a car yet. The rebuilt brushes are in the spare parts kit that goes on trips. My brushes have stranded me twice on long trips >:-|

I would like to hear feed back from others if they know some better tricks to rebuilding these brushes.

Don McMahon - BMWCCA #77764 86 535i; 85 535i; 75 3.0Si; 72 911T; 64 VW-Sedan 113 - I don't know when to let go

><snip>I removed the rectifier pack from the rear
>of the BOSCH alternator on my E28 1986 5'er. The brushes are
>quite short and look as though they have a copper core inset
>into the carbon brush - these hard cores look dangerously
>close to becoming exposed and scoring the amerture.
>
>Anyway the brushes look as though they have a soldered
>pig-tail and I have obtained some replacements from a BOSCH
>retailer for 3.5 UK. Has anyone ever changed these - the
>solder doesn't seem to melt with a soldering iron and if I
>am scared to use a blow-torch in case the plastic moulding
>melts.<snip>