Alternator brushes question

Hey Folks,
After going through everything electrical looking for what was blowing my 20 amp fuse, I checked the new alternator brushes I had installed and found the holder plate screwed in up side down.. When I unplugged the alternator connector and turned the key on the fuse didn't blow. So, I ordered another set from XJ4ever and was able to ride after installing them correctly. But then after about 40 miles it died again. I opened it up and found that the brush that contacts the inner ring of the rotor face had been ground down to 1/8" sticking out. While the other one looked like brand new. Both of them were not hanging up and the spring action was still working fine. I did clean the rotor face until it shined brightly using 400 grit and electrical cleaner before I installed the new brushes. It seemed like they contacted the Rotor face just fine. There was 1/16" wiggle from side to side. Is that normal? Also, just to clarify what happened to that brush. There were no pieces just alot of carbon dust. Maybe I switched the GR and BRN wire connections to the brushes. Could that cause one brush to desinegrate like that? Any help is greatly appreciated! Thanks, Ricksta

 

WOW! Rotor ate one and didn't eat the other? VERY bizarre! It is possible that the manufacturer got a bad batch of brushes and you were the lucky recipient of one of them. If they don't press the carbon matrix together hard enough, it bakes out to a very porous solid that is easily worn away. The wiggle room you describe on the brushes sounds normal to me. Pop a new brush in there and see what happens.

 

Thanks for the info Robert,
Polock thought that if I got the wires switched that one of the brushes could heat up. I did put them back the way they were, using a piece of masking tape. But, the bike has had an electrical problem since I got it. So, the PO could have switched them. I really want to make sure the wiring is correct this time. Do you know which wire, the green or the brown, connects to the brush with it's mounting screw on the left, looking at the brush mounting side of the holder plate, with the wire holder hole to the top? It's the brush with the mounting screw right next to it. I had the green wire hooked to that one. Any info would be appreciated. 1981 Maxim XJ 550. Ricksta