This is the same approach you would take to lube or replace the bearings.
The armature should be removable at this point. Now heat up your soldering iron and get ready to remove the brushes. When the iron is hot, unsolder the braided wire coming out of the side of the brush, and pull it free from the brush carrier. The brush is now loose. Remove it, and the spring that presses it against the armature. If you can locate factory brushes, put them in and solder them back in place, and you are done. If you could not locate factory brushes, read on...
The goal is to get brushes that match the old ones as closely as possible. Home Depot has some in stock which are rectangular and 1/8 inch too long. They are 1/16 inch too wide (that is the dimension that makes them rectangular instead of square) but they are exactly the right width. Get them. Never mind that the wire comes out of the end of the brush instead of the side.
I used a very small bench vise to clamp the brushes in horizontally with the offending 1/8 and 1/16 inch overages "showing" above and out the side of the vise. A few minutes with a hacksaw and a file resulted in a prefect replacement.
Now the tricky part is to bend the end of the brush carrier into a "V" so the wire comes out the end of the brush carries instead of the side. Here is a side view:
Before:
Brush
V Slot
______/____
===|_____/ |
===|___________|
BASEBASEBASEBASEBASE
After:
Brush
V Slot
______/____
===|_____/ \ <--Note the end of the brush carrier is "bowed" out
===|___________/
BASEBASEBASEBASEBASE
By bending the end of carries out in the "middle" and leaving it in at the
top and bottom, the spring will still be contained, but the wire can come
out the little opening created by the bent end plate. Unsolder the
contacts from the brushes, remove the springs, and thread the new brushes
into the carriers. Check for free movement, and make sure the mesh wires
do not bind in the little opening as the brush moves in and out. I pushed
a little extra wire into the carrier so the brush would be able to move
some without pulling on it.
Now clean the armature. Don't use anything that can remain behind and corrode the copper. I used 600 grit carbide wet/dry sandpaper - VERY CAREFULLY. I cleaned it all up and started soldering the brushes back in. Make sure you use "electronic" solder - with the rosin core. Then I reassembled the motor and tested it - YES!
One final suggestion. Do not use the high setting until the brushes have "worn in" a bit - it will reduce arcing and preserve your nice armature polish. I drove to work and back (30 miles round trip) a few dozen times before I tried "high." The brushes are working perfectly, the flat spot is gone, and high is HIGH.
David Butcher davidbu at www.los-gatos.ca.us Tel (408) 978-5495 Los Gatos, California 95030