Motor smells - like burning when running - is failure imminent?

[Fencer503]

My 725 drill has had a  hard life - it now smells like burning from the brushes when running. Will new brushes help or is the armature doomed?.... cheers

[kanxrus]

First off I Highly recommend taking your drill to a Authorized Dewalt Service Center. However if you plan on doing work yourself, here is what I would look for.

If you don't have good contact between the brushes and armature you will get an arc of electricity. This can cause burning, and premature wear. When you pull the trigger, do you see a lot of excessive sparking?

Brushes do wear overtime and is usually a good place to start. If you've worked the drill extremely hard, I would check the armature for pitting. If the armature looks good, and your brushes are not completely worn down. Check the bottom of the brushes for pitting as well. If you see pitting (after the drill has been taken apart), I would recommend sanding the brushes lightly with emery paper, or simply buy a new pair. They are very cheap.

They will run you around $3.00 Dewalt Part number's N031376, N031377.

Here is a look inside the Dewalt DC720, identical drill without the hammer function. http://dewaltownersgroup.com/index.php/topic,27.0.html

[dtsman]

My DC989 18vXRP drill was doing that. I bought an almost new DC950 drill off Craigslist to replace it. So with nothing to lose, I gave the well used 989 a tune up and that fixed it. Here is what I did.

  I took it completely apart, cleaned the yellow plastics with Mister Clean Magic eraser and toothbrush with soap, wiped out all the old grease and regreased all the gearing. For the motor smoking and stinking, I sprayed the end with the brushes well with carburator cleaner, (electrical contact cleaner would be the correct chemical, probably) and flushed black soot out of it while spining the motor with my other hand, blew out with compressed air, and repated until cleaner flushed clear. I was careful not to get any up inside the motor on the coiled part. Again blew dry with air compressor, or canned air.

  The drill is back together, it looks and runs like new. No smell, no smoke, and no sparks!!

The brushes appear to be exposed on the ends of these drills through the grill portions of the case. This process may be able to be done without disassembly, but can not confirm that.

Bo

Houston, TX