I was drilling a hole in the wall with my 1984 vintage Bosch CSB 470-RLE impact drill, when it suddenly gave out. I figured the stone was too hard, increased the power on the potmeter and it worked for a couple of seconds until finally stopping. I didn't smell any 'electrons' or other burning scents.

Now I can't get it to rotate again.

I've watched some youtube instructions for fixing common failure mechanisms, such as failure of the electrical switch as well as expiration of the coal brushes. However, I find a voltage on the commutator as well as on the coal brushes (i.e. electrical contact is sufficient) when I press the electrical switch (i.e. switch not broken). I took out the coal brushes and they are still about ~2 cm or 0.75" long, more than sufficient I would think.

Does anybody have a suggestion on a possible root cause for the motor no longer working?

Opened up 1984 Bosch impact drill

  • Hello, and welcome to Stack Exchange. Despite the "DIY" URL, this question may not be a good fit for our "Home Improvement" theme. – Daniel Griscom Jul 24 '16 at 14:02
  • I agree, as there are not many similar articles in this exchange. However, I did not find a more suitable one. Do you have any suggestions? – skleijn Jul 24 '16 at 14:09
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    I don't know of a better place; hopefully you get a good response here. – Daniel Griscom Jul 24 '16 at 15:00
  • You don't read the voltage of the brushes, you look at the remaining carbon, if fully extended per example, the brushes aren't extending by at least 50% of the housing it's probably time to change them(the housing is typically the same size as the carbon brush. The brushes will typically not stop an audible reaction to hitting the trigger. Also, test for continuity through the trigger, not just voltage, failure typically is due to solder joints arc'ing or corroding.. – Chris Jul 24 '16 at 15:57
  • Thanks Chris, I've ordered some replacement brushes. Hope that's the issue. The solder joints look pretty good and I've checked for continuity. However; you don't hear anything when hitting the trigger... – skleijn Jul 24 '16 at 17:39

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