# dirty com bars



## major (Apr 4, 2008)

mi7d1 said:


> Taking a peak at my com bar, I noticed some bridging. Didn't want to touch it till I got some advice. The motor is a 6.7" Advanced DC A00-4009. Think I have some carbon dust fouling going on since I have voltage reading to the vehicle frame. The voltage reading is what prompted me to look at the brushes and com bar.


From here it looks like some arcing has been going on. Maybe a little copper erosion but mostly carbon smear. A proper comm turning and undercut would be best and then a full break-in period. Or you could get a comm dressing stone sometimes (incorrectly) called a brush seating stone, use it, blow/vacuum out the motor and clear the comm mica slots with a dental pick.

Before you do anything, I'd suggest you run it and take some data---V, I & RPM and watch for arcing (maybe with a video). Try to determine why it is in that state. I'd guess it is overloaded.


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## mi7d1 (May 19, 2010)

*Re: dirty comm bars*

Thank you for the reply. I had a look at the Brush/Commutator Wear Guide link you had posted in another thread and it seems as if carbon smear may be the precursor to streaking. Could weak brush springs or dirty brush guides cause or contribute to the smearing? They would both contribute to arcing. The vehicle had sat unused for over two years with two of those years (my ownership) being out in the elements. I've ran it for around 100 miles since.

With my skill levels and electrical understanding I think it's best to look for a motor repair shop here in Portland and let them service the motor. Basic wiring I can do if given clear instructions but motors are a new unknown.


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## Ziggythewiz (May 16, 2010)

mi7d1 said:


> Think I have some carbon dust fouling going on since I have voltage reading to the vehicle frame.


Have you checked your gauges? It's common for those to lack isolation.


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## mi7d1 (May 19, 2010)

Ziggythewiz said:


> Have you checked your gauges? It's common for those to lack isolation.


It was my KSI wire to be specific. The reading was around 44 volts. The KSI voltage is 12V out of my DC converter. I did a little cleaning on the brushes and now the KSI reads 12V. Not sure if the cleaning caused the change or what happened. Unless I've missed a setting in the programing, my Alltrax SPM requires pack voltage for the KSI. I've had the vehicle moving in my driveway under it's own power but need to clean out the carbon dust before I take it to the street. At this time I'm in the process of removing the motor.


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## Clarence (Oct 31, 2012)

I have this problem after one to two month and i have get better idea now in this thread.I want to asked to anyone when i start the car then i feel something noise from Radiator side.


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