Archived from the Tools In Action forum (Dewalt). This thread is read-only.
I have a DC987 drill that is about four or five years old now, and it’s been used pretty hard. Whenever the drill is run, even when not under any load, and in any gear, it gives off a hot electricity smell. Like smoldering plastic or something similar. I pulled the back cover off and checked the brushes, and they seem to be fine, about 1/2″ long. There was some carbon dust in the housing that I just blew out with compressed air, but the problem continues. Is this caused by brushes or was the motor overheated and partially melted, or something completely different?
I would check the connections in the trigger area to make sure they are not shorting out.
This is just a guess without actually seeing it.
If the brushes are kept clear of debri, theu can cause hot spot’s, or pitting on the armature surface. Everytime the brush rolls over a surface that is not flat you will see an arch flash. This is what causes the burning smell, it will lead to pre-mature failure of the motor. A new can motor for the DC987 about $38. If you have a Dewalt owned Service center near by, you can have them take a peek.
Well, I took it apart the trigger was just dusty but I wiped it off and it seemed fine. The inside of the plastic housing had a light coating of greasy sawdust and I cleaned everything out. Then putting it back together, the transmission decided to fall apart, what a fun job it was figuring out how that goes together. I got it all back together new grease and It seems to be a less noticeable smell, but its still there, especially if you load the drill up at all. It does seem to really spark more than normal, what causes the armature to be pitted? It sounds like you said that keeping it clean actually causes pitting? Is it really just that worn, or should the brushes be replaced?
It looks like you can get the parts cheap from here http://www.ereplacementparts.com/dewalt-dc987-type-18v-cordless-drill-parts-c-1009_1162_2836.html I would replace the brushes.
If you have pitting on the Armature, then replacing the brushes won’t do anything.
Well that website toolacious posted wants 38 bucks for a motor and brushes so that’s the route I’ll go if it gets any worse. What causes pitting in the armature? Is the DC987 a good unit in comparison to other older/newer DeWalts?
The “new” DCD970 is a better drill in many ways. Improvments in comfort, balance and in my opinion better ratio on the different gears. But why buy a new drill if the old one works or just need a little money on service? The dc987 is a solid drill that will be competitive for some more years. I bought a DCD960 because my old 12v dewalt started to be a little to weak and my batteries had lost something like 40 percent runtime. The batteries to that machine was to expensive compared to the drill itself. In my opinion that is not the case with the more profesionel drills like DCD970 or the old DC987. If a battery is bad it is worth to buy a new battery or put some money on service.