Some DC motors have a characteristic smell when they run, and today I started wondering what it would be. I noticed it many years ago for some train scale models (probably Märklin), some years later on my father's power drill (handheld, AC powered). Back then I assumed it had something to do with the sparks in there. Now my brushless (and sparkless) cordless drill, a Bosch GSB 10,8, has the same smell when running; another one, DRC 18/4 from Festool, much less so.

The smell is hard to describe, it is not something like a solvent or grease or something that is melting. I’d also say it is strongest for the first few seconds after some idle days.

  • \$\begingroup\$ Burning dust, most likely. \$\endgroup\$
    – Hearth
    Commented Sep 17, 2022 at 17:22
  • 5
    \$\begingroup\$ Does it perhaps smell like a that rainy day smell? If so, that's smell of ozone generated by sparks in the air. \$\endgroup\$
    – DKNguyen
    Commented Sep 17, 2022 at 17:29
  • 1
    \$\begingroup\$ It sounds like the lubrication used in the unit, oil or grease. \$\endgroup\$
    – Gil
    Commented Sep 17, 2022 at 17:56
  • \$\begingroup\$ @DKNguyen ozone is the answer combined with hot varnish on the coils. \$\endgroup\$
    – D Duck
    Commented Sep 17, 2022 at 18:16
  • \$\begingroup\$ I'm with @DDuck and the hot varnish. \$\endgroup\$
    – Transistor
    Commented Sep 17, 2022 at 19:10


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