# Best Way to Clean Motor Brushes and Commutator?



## maxstang (Sep 20, 2008)

In my continuing struggle to get a Rabbit conversion back on the road, I've run into a problem. 

Motor spun up fine in neutral but on the first test drive, after a block or so, I had audible sparking at the brushes and the motor would refuse to spin up if it stopped in certain positions (meaning the brushes were in certain positions on the commutator). This is an Advance DC 9" motor and the car has been sitting for 5 years outside, but covered. I'm assuming that I have corrosion on commutator that is preventing good contact under high amp loads. I have yet to take it apart and look to confirm (it's over 100 here today!). Assuming I'm correct, what would be the best way to clean the commutator and brushes? Thanks for your help.


----------



## TX_Dj (Jul 25, 2008)

The brushes are probably fine, if they're not damaged (which could be, depending on what kind of stuff they were contacting and the arcing).

The commutator on the other hand, if it's not pitted, you can probably clean it up with a strip of emory paper and some elbow grease. Be gentle with it, the point is to buff off any corrosion, not to cause significant change to the size of the comm bars.

Someone else probably has a better idea.


----------



## major (Apr 4, 2008)

TX_Dj said:


> Someone else probably has a better idea.


I recommend he take it to a pro. Or at minimum, take some good photos and post up here. Let's see what we're dealing with.

major


----------



## TX_Dj (Jul 25, 2008)

Definitely taking it to a pro is the best option, but this is DIY after all. 

Something that big, it's probably best to take it to a pro unless you've done this sort of thing before. I've never done any internal work on anything that large, so take my advice with a grain of salt.


----------



## maxstang (Sep 20, 2008)

Thanks guys. I'll try and get some good pics of it tomorrow. I've done smaller motors with emery paper, but never anything this big. REALLY don't want to have to take the motor out. That would be a major pain.


----------



## EVfun (Mar 14, 2010)

The phrase of the day is "commutator stone"  It is the way to evenly smooth the commutator while running the motor. The other thing to check is that all the brushes are freely able to move in their holders and that none of the brush springs are broken. 

After the amount of time your motor has been sitting, I recommend removing each pair of brushes and use an old toothbrush to clean the holders and outside of the brushes. Check the running end of the brushes to make sure it hasn't been blown away by arcing. If the brushes are damaged or worn down to near the rivet in them they should be replaced. With the brushes freely working the motor should be run at a low to moderate rpm and the commutator should be gently stoned, just enough to bring up bright copper. The stone will let you reach in and sand the comm with the motor assembled. If you have decent access to the brushes you should be able to do all the stuff I've suggested without any disassembly except for taking the brush lead screws out to lift out the brushes.


----------



## maxstang (Sep 20, 2008)

Thanks for the great reply. I did some disassembly today and the brushes were all frozen in their guides. I've pulled a couple of them out, but will have to work hard to free the others. Looks like the brush guides had corrosion. I'll take some close up pictures of both the guides and the brushes. The brushes are worn and there's a significant amount of brush material on the com. I'm hoping I can get the other brushes out without destroying them. 

Was there a lubricant or coating on the inside of the brush guides? It looks like there was a black coating there, that has peeled off in places due to corrosion. 

I'm assuming I can clean the corrosion off the brushes and reuse them. I've ordered a com stone and will see what I can manage cleaning it. -M


----------

