Komatsu FR15DR2A:
Drive Motor Brushes jumping on Commentator

Drive motor is making a strange sound (clicking). When I pulled off fan and looked in. I could visually see brushes jumping off segments. Prior to this motor over heated and carbon that was in windings got hot enough to start smoldering. I blew out motor it ran but then noticed the noise.
  • Posted 14 Aug 2015 03:18
  • Discussion started by twoeey
  • Pennsylvania, United States
Showing items 1 - 6 of 6 results.
go back to the motor and look at the armature bars real close.
that glowing you saw was the residue or possibly a chunk of copper off one of the bars shorting against the next bar.
There is one critical step alot of guys forget to do or just don't know to do and that is to clean out the gaps if your doing alot of resurfacing and then following up with a polishing stone.
So go in and check between each bar and make sure there are no bridges of copper built up. You can take a tool they make for cleaning the gaps and truing up the edges of the bars to make a clean gap.
  • Posted 21 Jan 2021 09:21
  • Reply by swoop223
  • North Carolina, United States
You've been swooped!
swoop223@gmail.com
I stoned the commentators on motors for years , with hit and miss results. yesterday I stoned one on a RD5200 Crown. The way I do it is to jack up the truck , pull one set of the brushes out , start motor running and stone the commentator.
Then all of a sudden it stopped and I saw a red glow in the motor just past the brush holder. I shut it off real quick , but now when I start it up it says "Please stand by" for about 20 seconds and the codes out to a 329 and 321.
Following the book I checked the modules 2 and 3 and they checked good.
I blew the motor out real good to, still no start.
  • Posted 21 Jan 2021 06:15
  • Reply by BigAl88246
  • North Carolina, United States
Thanks Swoop. Have ordered new motor.
  • Posted 15 Aug 2015 02:59
  • Reply by twoeey
  • Pennsylvania, United States
you can try to rebuild the motor but 9 times out of 10 the armature is generally trashed and would also have to be replaced, the expense of this is almost the cost of a new motor.

You can try to resurface the armature commentator but you will find after a short period of time the 'clicking' will return even under normal operation and cause drive error codes relating to open drive circuits because the brushes will start jumping off the bars again.

If you take a closer look at these sections that are raised you will find they correspond to where the brushes are related to their positions around the brush housing. This 'raised com bar' scenario is caused by stalling the motor usually. The com bars get hot, the resin that holds them together gets soft, the bars raise up from the centrifugal force being applied when the armature is turning. Once this happens there is no 'fix' for this, it will continue to happen until the com bars just short out or come apart.

using a seating brush or resurfacing stone or even rebuilding the motor and cutting the armature com bar surface down may temporarily fix this problem but the 'real fix' is to just replace the armature or complete motor.
  • Posted 14 Aug 2015 20:43
  • Modified 14 Aug 2015 20:45 by poster
  • Reply by swoop223
  • North Carolina, United States
You've been swooped!
swoop223@gmail.com
Thanks Alanmitsi. Will rerbuild.
  • Posted 14 Aug 2015 05:20
  • Reply by twoeey
  • Pennsylvania, United States
Commutator has a high segment could try a skim but if its let go will need a new one
  • Posted 14 Aug 2015 04:30
  • Reply by alanmitsi
  • essex, United Kingdom

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